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| * | | | sched/numa: Fix is_core_idle()Mika Penttilä2021-08-041-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Use the loop variable instead of the function argument to test the other SMT siblings for idle. Fixes: ff7db0bf24db ("sched/numa: Prefer using an idle CPU as a migration target instead of comparing tasks") Signed-off-by: Mika Penttilä <mika.penttila@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Pankaj Gupta <pankaj.gupta@ionos.com> Link: https://lkml.kernel.org/r/20210722063946.28951-1-mika.penttila@gmail.com
| * | | | sched: Optimize housekeeping_cpumask() in for_each_cpu_and()Yuan ZhaoXiong2021-06-282-4/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | On a 128 cores AMD machine, there are 8 cores in nohz_full mode, and the others are used for housekeeping. When many housekeeping cpus are in idle state, we can observe huge time burn in the loop for searching nearest busy housekeeper cpu by ftrace. 9) | get_nohz_timer_target() { 9) | housekeeping_test_cpu() { 9) 0.390 us | housekeeping_get_mask.part.1(); 9) 0.561 us | } 9) 0.090 us | __rcu_read_lock(); 9) 0.090 us | housekeeping_cpumask(); 9) 0.521 us | housekeeping_cpumask(); 9) 0.140 us | housekeeping_cpumask(); ... 9) 0.500 us | housekeeping_cpumask(); 9) | housekeeping_any_cpu() { 9) 0.090 us | housekeeping_get_mask.part.1(); 9) 0.100 us | sched_numa_find_closest(); 9) 0.491 us | } 9) 0.100 us | __rcu_read_unlock(); 9) + 76.163 us | } for_each_cpu_and() is a micro function, so in get_nohz_timer_target() function the for_each_cpu_and(i, sched_domain_span(sd), housekeeping_cpumask(HK_FLAG_TIMER)) equals to below: for (i = -1; i = cpumask_next_and(i, sched_domain_span(sd), housekeeping_cpumask(HK_FLAG_TIMER)), i < nr_cpu_ids;) That will cause that housekeeping_cpumask() will be invoked many times. The housekeeping_cpumask() function returns a const value, so it is unnecessary to invoke it every time. This patch can minimize the worst searching time from ~76us to ~16us in my testing. Similarly, the find_new_ilb() function has the same problem. Co-developed-by: Li RongQing <lirongqing@baidu.com> Signed-off-by: Li RongQing <lirongqing@baidu.com> Signed-off-by: Yuan ZhaoXiong <yuanzhaoxiong@baidu.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/1622985115-51007-1-git-send-email-yuanzhaoxiong@baidu.com
| * | | | sched/sysctl: Move extern sysctl declarations to sched.hHailong Liu2021-06-281-0/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Since commit '8a99b6833c88(sched: Move SCHED_DEBUG sysctl to debugfs)', SCHED_DEBUG sysctls are moved to debugfs, so these extern sysctls in include/linux/sched/sysctl.h are no longer needed for sysctl.c, even some are no longer needed. So move those extern sysctls that needed by kernel/sched/debug.c to kernel/sched/sched.h, and remove others that are no longer needed. Signed-off-by: Hailong Liu <liu.hailong6@zte.com.cn> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210606115451.26745-1-liuhailongg6@163.com
| * | | | sched/debug: Don't update sched_domain debug directories before ↵Valentin Schneider2021-06-281-0/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | sched_debug_init() Since CPU capacity asymmetry can stem purely from maximum frequency differences (e.g. Pixel 1), a rebuild of the scheduler topology can be issued upon loading cpufreq, see: arch_topology.c::init_cpu_capacity_callback() Turns out that if this rebuild happens *before* sched_debug_init() is run (which is a late initcall), we end up messing up the sched_domain debug directory: passing a NULL parent to debugfs_create_dir() ends up creating the directory at the debugfs root, which in this case creates /sys/kernel/debug/domains (instead of /sys/kernel/debug/sched/domains). This currently doesn't happen on asymmetric systems which use cpufreq-scpi or cpufreq-dt drivers, as those are loaded via deferred_probe_initcall() (it is also a late initcall, but appears to be ordered *after* sched_debug_init()). Ionela has been working on detecting maximum frequency asymmetry via ACPI, and that actually happens via a *device* initcall, thus before sched_debug_init(), and causes the aforementionned debugfs mayhem. One option would be to punt sched_debug_init() down to fs_initcall_sync(). Preventing update_sched_domain_debugfs() from running before sched_debug_init() appears to be the safer option. Fixes: 3b87f136f8fc ("sched,debug: Convert sysctl sched_domains to debugfs") Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: http://lore.kernel.org/r/20210514095339.12979-1-ionela.voinescu@arm.com
* | | | | Merge branch 'core-rcu.2021.08.28a' of ↵Linus Torvalds2021-08-301-0/+11
|\ \ \ \ \ | |_|_|_|/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu Pull RCU updates from Paul McKenney: "RCU changes for this cycle were: - Documentation updates - Miscellaneous fixes - Offloaded-callbacks updates - Updates to the nolibc library - Tasks-RCU updates - In-kernel torture-test updates - Torture-test scripting, perhaps most notably the pinning of torture-test guest OSes so as to force differences in memory latency. For example, in a two-socket system, a four-CPU guest OS will have one pair of its CPUs pinned to threads in a single core on one socket and the other pair pinned to threads in a single core on the other socket. This approach proved able to force race conditions that earlier testing missed. Some of these race conditions are still being tracked down" * 'core-rcu.2021.08.28a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (61 commits) torture: Replace deprecated CPU-hotplug functions. rcu: Replace deprecated CPU-hotplug functions rcu: Print human-readable message for schedule() in RCU reader rcu: Explain why rcu_all_qs() is a stub in preemptible TREE RCU rcu: Use per_cpu_ptr to get the pointer of per_cpu variable rcu: Remove useless "ret" update in rcu_gp_fqs_loop() rcu: Mark accesses in tree_stall.h rcu: Make rcu_gp_init() and rcu_gp_fqs_loop noinline to conserve stack rcu: Mark lockless ->qsmask read in rcu_check_boost_fail() srcutiny: Mark read-side data races rcu: Start timing stall repetitions after warning complete rcu: Do not disable GP stall detection in rcu_cpu_stall_reset() rcu/tree: Handle VM stoppage in stall detection rculist: Unify documentation about missing list_empty_rcu() rcu: Mark accesses to ->rcu_read_lock_nesting rcu: Weaken ->dynticks accesses and updates rcu: Remove special bit at the bottom of the ->dynticks counter rcu: Fix stall-warning deadlock due to non-release of rcu_node ->lock rcu: Fix to include first blocked task in stall warning torture: Make kvm-test-1-run-qemu.sh check for reboot loops ...
| * | | | rcu: Explain why rcu_all_qs() is a stub in preemptible TREE RCUFrederic Weisbecker2021-08-061-0/+11
| | |_|/ | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The cond_resched() function reports an RCU quiescent state only in non-preemptible TREE RCU implementation. This commit therefore adds a comment explaining why cond_resched() does nothing in preemptible kernels. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Cc: Neeraj Upadhyay <neeraju@codeaurora.org> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Uladzislau Rezki <urezki@gmail.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* | | | sched: Fix get_push_task() vs migrate_disable()Sebastian Andrzej Siewior2021-08-261-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | push_rt_task() attempts to move the currently running task away if the next runnable task has migration disabled and therefore is pinned on the current CPU. The current task is retrieved via get_push_task() which only checks for nr_cpus_allowed == 1, but does not check whether the task has migration disabled and therefore cannot be moved either. The consequence is a pointless invocation of the migration thread which correctly observes that the task cannot be moved. Return NULL if the task has migration disabled and cannot be moved to another CPU. Fixes: a7c81556ec4d3 ("sched: Fix migrate_disable() vs rt/dl balancing") Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210826133738.yiotqbtdaxzjsnfj@linutronix.de
* | | | sched: Fix Core-wide rq->lock for uninitialized CPUsPeter Zijlstra2021-08-202-27/+118
| |_|/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Eugene tripped over the case where rq_lock(), as called in a for_each_possible_cpu() loop came apart because rq->core hadn't been setup yet. This is a somewhat unusual, but valid case. Rework things such that rq->core is initialized to point at itself. IOW initialize each CPU as a single threaded Core. CPU online will then join the new CPU (thread) to an existing Core where needed. For completeness sake, have CPU offline fully undo the state so as to not presume the topology will match the next time it comes online. Fixes: 9edeaea1bc45 ("sched: Core-wide rq->lock") Reported-by: Eugene Syromiatnikov <esyr@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Josh Don <joshdon@google.com> Tested-by: Eugene Syromiatnikov <esyr@redhat.com> Link: https://lkml.kernel.org/r/YR473ZGeKqMs6kw+@hirez.programming.kicks-ass.net
* | | sched/rt: Fix double enqueue caused by rt_effective_prioPeter Zijlstra2021-08-041-55/+35
|/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Double enqueues in rt runqueues (list) have been reported while running a simple test that spawns a number of threads doing a short sleep/run pattern while being concurrently setscheduled between rt and fair class. WARNING: CPU: 3 PID: 2825 at kernel/sched/rt.c:1294 enqueue_task_rt+0x355/0x360 CPU: 3 PID: 2825 Comm: setsched__13 RIP: 0010:enqueue_task_rt+0x355/0x360 Call Trace: __sched_setscheduler+0x581/0x9d0 _sched_setscheduler+0x63/0xa0 do_sched_setscheduler+0xa0/0x150 __x64_sys_sched_setscheduler+0x1a/0x30 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae list_add double add: new=ffff9867cb629b40, prev=ffff9867cb629b40, next=ffff98679fc67ca0. kernel BUG at lib/list_debug.c:31! invalid opcode: 0000 [#1] PREEMPT_RT SMP PTI CPU: 3 PID: 2825 Comm: setsched__13 RIP: 0010:__list_add_valid+0x41/0x50 Call Trace: enqueue_task_rt+0x291/0x360 __sched_setscheduler+0x581/0x9d0 _sched_setscheduler+0x63/0xa0 do_sched_setscheduler+0xa0/0x150 __x64_sys_sched_setscheduler+0x1a/0x30 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae __sched_setscheduler() uses rt_effective_prio() to handle proper queuing of priority boosted tasks that are setscheduled while being boosted. rt_effective_prio() is however called twice per each __sched_setscheduler() call: first directly by __sched_setscheduler() before dequeuing the task and then by __setscheduler() to actually do the priority change. If the priority of the pi_top_task is concurrently being changed however, it might happen that the two calls return different results. If, for example, the first call returned the same rt priority the task was running at and the second one a fair priority, the task won't be removed by the rt list (on_list still set) and then enqueued in the fair runqueue. When eventually setscheduled back to rt it will be seen as enqueued already and the WARNING/BUG be issued. Fix this by calling rt_effective_prio() only once and then reusing the return value. While at it refactor code as well for clarity. Concurrent priority inheritance handling is still safe and will eventually converge to a new state by following the inheritance chain(s). Fixes: 0782e63bc6fe ("sched: Handle priority boosted tasks proper in setscheduler()") [squashed Peterz changes; added changelog] Reported-by: Mark Simmons <msimmons@redhat.com> Signed-off-by: Juri Lelli <juri.lelli@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210803104501.38333-1-juri.lelli@redhat.com
* | Merge tag 'sched-urgent-2021-07-11' of ↵Linus Torvalds2021-07-112-10/+18
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler fixes from Ingo Molnar: "Three fixes: - Fix load tracking bug/inconsistency - Fix a sporadic CFS bandwidth constraints enforcement bug - Fix a uclamp utilization tracking bug for newly woken tasks" * tag 'sched-urgent-2021-07-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/uclamp: Ignore max aggregation if rq is idle sched/fair: Fix CFS bandwidth hrtimer expiry type sched/fair: Sync load_sum with load_avg after dequeue
| * | sched/uclamp: Ignore max aggregation if rq is idleXuewen Yan2021-07-021-7/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When a task wakes up on an idle rq, uclamp_rq_util_with() would max aggregate with rq value. But since there is no task enqueued yet, the values are stale based on the last task that was running. When the new task actually wakes up and enqueued, then the rq uclamp values should reflect that of the newly woken up task effective uclamp values. This is a problem particularly for uclamp_max because it default to 1024. If a task p with uclamp_max = 512 wakes up, then max aggregation would ignore the capping that should apply when this task is enqueued, which is wrong. Fix that by ignoring max aggregation if the rq is idle since in that case the effective uclamp value of the rq will be the ones of the task that will wake up. Fixes: 9d20ad7dfc9a ("sched/uclamp: Add uclamp_util_with()") Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> [qias: Changelog] Reviewed-by: Qais Yousef <qais.yousef@arm.com> Link: https://lore.kernel.org/r/20210630141204.8197-1-xuewen.yan94@gmail.com
| * | sched/fair: Fix CFS bandwidth hrtimer expiry typeOdin Ugedal2021-07-021-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The time remaining until expiry of the refresh_timer can be negative. Casting the type to an unsigned 64-bit value will cause integer underflow, making the runtime_refresh_within return false instead of true. These situations are rare, but they do happen. This does not cause user-facing issues or errors; other than possibly unthrottling cfs_rq's using runtime from the previous period(s), making the CFS bandwidth enforcement less strict in those (special) situations. Signed-off-by: Odin Ugedal <odin@uged.al> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Ben Segall <bsegall@google.com> Link: https://lore.kernel.org/r/20210629121452.18429-1-odin@uged.al
| * | sched/fair: Sync load_sum with load_avg after dequeueVincent Guittot2021-07-021-1/+2
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 9e077b52d86a ("sched/pelt: Check that *_avg are null when *_sum are") reported some inconsitencies between *_avg and *_sum. commit 1c35b07e6d39 ("sched/fair: Ensure _sum and _avg values stay consistent") fixed some but one remains when dequeuing load. sync the cfs's load_sum with its load_avg after dequeuing the load of a sched_entity. Fixes: 9e077b52d86a ("sched/pelt: Check that *_avg are null when *_sum are") Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Odin Ugedal <odin@uged.al> Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Link: https://lore.kernel.org/r/20210701171837.32156-1-vincent.guittot@linaro.org
* | Merge tag 'pm-5.14-rc1-2' of ↵Linus Torvalds2021-07-071-0/+1
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm Pull more power management updates from Rafael Wysocki: "These include cpufreq core simplifications and fixes, cpufreq driver updates, cpuidle driver update, a generic power domains (genpd) locking fix and a debug-related simplification of the PM core. Specifics: - Drop the ->stop_cpu() (not really useful) and ->resolve_freq() (unused) cpufreq driver callbacks and modify the users of the former accordingly (Viresh Kumar, Rafael Wysocki). - Add frequency invariance support to the ACPI CPPC cpufreq driver again along with the related fixes and cleanups (Viresh Kumar). - Update the Meditak, qcom and SCMI ARM cpufreq drivers (Fabien Parent, Seiya Wang, Sibi Sankar, Christophe JAILLET). - Rename black/white-lists in the DT cpufreq driver (Viresh Kumar). - Add generic performance domains support to the dvfs DT bindings (Sudeep Holla). - Refine locking in the generic power domains (genpd) support code to avoid lock dependency issues (Stephen Boyd). - Update the MSM and qcom ARM cpuidle drivers (Bartosz Dudziak). - Simplify the PM core debug code by using ktime_us_delta() to compute time interval lengths (Mark-PK Tsai)" * tag 'pm-5.14-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (21 commits) PM: domains: Shrink locking area of the gpd_list_lock PM: sleep: Use ktime_us_delta() in initcall_debug_report() cpufreq: CPPC: Add support for frequency invariance arch_topology: Avoid use-after-free for scale_freq_data cpufreq: CPPC: Pass structure instance by reference cpufreq: CPPC: Fix potential memleak in cppc_cpufreq_cpu_init cpufreq: Remove ->resolve_freq() cpufreq: Reuse cpufreq_driver_resolve_freq() in __cpufreq_driver_target() cpufreq: Remove the ->stop_cpu() driver callback cpufreq: powernv: Migrate to ->exit() callback instead of ->stop_cpu() cpufreq: CPPC: Migrate to ->exit() callback instead of ->stop_cpu() cpufreq: intel_pstate: Combine ->stop_cpu() and ->offline() cpuidle: qcom: Add SPM register data for MSM8226 dt-bindings: arm: msm: Add SAW2 for MSM8226 dt-bindings: cpufreq: update cpu type and clock name for MT8173 SoC clk: mediatek: remove deprecated CLK_INFRA_CA57SEL for MT8173 SoC cpufreq: dt: Rename black/white-lists cpufreq: scmi: Fix an error message cpufreq: mediatek: add support for mt8365 dt-bindings: dvfs: Add support for generic performance domains ...
| * | cpufreq: CPPC: Add support for frequency invarianceViresh Kumar2021-07-011-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The Frequency Invariance Engine (FIE) is providing a frequency scaling correction factor that helps achieve more accurate load-tracking. Normally, this scaling factor can be obtained directly with the help of the cpufreq drivers as they know the exact frequency the hardware is running at. But that isn't the case for CPPC cpufreq driver. Another way of obtaining that is using the arch specific counter support, which is already present in kernel, but that hardware is optional for platforms. This patch updates the CPPC driver to register itself with the topology core to provide its own implementation (cppc_scale_freq_tick()) of topology_scale_freq_tick() which gets called by the scheduler on every tick. Note that the arch specific counters have higher priority than CPPC counters, if available, though the CPPC driver doesn't need to have any special handling for that. On an invocation of cppc_scale_freq_tick(), we schedule an irq work (since we reach here from hard-irq context), which then schedules a normal work item and cppc_scale_freq_workfn() updates the per_cpu arch_freq_scale variable based on the counter updates since the last tick. To allow platforms to disable this CPPC counter-based frequency invariance support, this is all done under CONFIG_ACPI_CPPC_CPUFREQ_FIE, which is enabled by default. This also exports sched_setattr_nocheck() as the CPPC driver can be built as a module. Cc: linux-acpi@vger.kernel.org Tested-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Ionela Voinescu <ionela.voinescu@arm.com> Tested-by: Qian Cai <quic_qiancai@quicinc.com> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
* | | Merge branch 'for-5.14' of ↵Linus Torvalds2021-07-011-13/+17
|\ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup Pull cgroup updates from Tejun Heo: - cgroup.kill is added which implements atomic killing of the whole subtree. Down the line, this should be able to replace the multiple userland implementations of "keep killing till empty". - PSI can now be turned off at boot time to avoid overhead for configurations which don't care about PSI. * 'for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cgroup: make per-cgroup pressure stall tracking configurable cgroup: Fix kernel-doc cgroup: inline cgroup_task_freeze() tests/cgroup: test cgroup.kill tests/cgroup: move cg_wait_for(), cg_prepare_for_wait() tests/cgroup: use cgroup.kill in cg_killall() docs/cgroup: add entry for cgroup.kill cgroup: introduce cgroup.kill
| * | | cgroup: make per-cgroup pressure stall tracking configurableSuren Baghdasaryan2021-06-081-13/+17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | PSI accounts stalls for each cgroup separately and aggregates it at each level of the hierarchy. This causes additional overhead with psi_avgs_work being called for each cgroup in the hierarchy. psi_avgs_work has been highly optimized, however on systems with large number of cgroups the overhead becomes noticeable. Systems which use PSI only at the system level could avoid this overhead if PSI can be configured to skip per-cgroup stall accounting. Add "cgroup_disable=pressure" kernel command-line option to allow requesting system-wide only pressure stall accounting. When set, it keeps system-wide accounting under /proc/pressure/ but skips accounting for individual cgroups and does not expose PSI nodes in cgroup hierarchy. Signed-off-by: Suren Baghdasaryan <surenb@google.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Tejun Heo <tj@kernel.org>
* | | | Merge tag 'sched-urgent-2021-06-30' of ↵Linus Torvalds2021-06-301-3/+3
|\ \ \ \ | | |_|/ | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler fixes from Ingo Molnar: - Fix a small inconsistency (bug) in load tracking, caught by a new warning that several people reported. - Flip CONFIG_SCHED_CORE to default-disabled, and update the Kconfig help text. * tag 'sched-urgent-2021-06-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/core: Disable CONFIG_SCHED_CORE by default sched/fair: Ensure _sum and _avg values stay consistent
| * | | sched/fair: Ensure _sum and _avg values stay consistentOdin Ugedal2021-06-281-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The _sum and _avg values are in general sync together with the PELT divider. They are however not always completely in perfect sync, resulting in situations where _sum gets to zero while _avg stays positive. Such situations are undesirable. This comes from the fact that PELT will increase period_contrib, also increasing the PELT divider, without updating _sum and _avg values to stay in perfect sync where (_sum == _avg * divider). However, such PELT change will never lower _sum, making it impossible to end up in a situation where _sum is zero and _avg is not. Therefore, we need to ensure that when subtracting load outside PELT, that when _sum is zero, _avg is also set to zero. This occurs when (_sum < _avg * divider), and the subtracted (_avg * divider) is bigger or equal to the current _sum, while the subtracted _avg is smaller than the current _avg. Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by: Odin Ugedal <odin@uged.al> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Link: https://lore.kernel.org/r/20210624111815.57937-1-odin@uged.al
* | | | Merge tag 'for-5.14/block-2021-06-29' of git://git.kernel.dk/linux-blockLinus Torvalds2021-06-301-2/+7
|\ \ \ \ | |_|_|/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pull core block updates from Jens Axboe: - disk events cleanup (Christoph) - gendisk and request queue allocation simplifications (Christoph) - bdev_disk_changed cleanups (Christoph) - IO priority improvements (Bart) - Chained bio completion trace fix (Edward) - blk-wbt fixes (Jan) - blk-wbt enable/disable fix (Zhang) - Scheduler dispatch improvements (Jan, Ming) - Shared tagset scheduler improvements (John) - BFQ updates (Paolo, Luca, Pietro) - BFQ lock inversion fix (Jan) - Documentation improvements (Kir) - CLONE_IO block cgroup fix (Tejun) - Remove of ancient and deprecated block dump feature (zhangyi) - Discard merge fix (Ming) - Misc fixes or followup fixes (Colin, Damien, Dan, Long, Max, Thomas, Yang) * tag 'for-5.14/block-2021-06-29' of git://git.kernel.dk/linux-block: (129 commits) block: fix discard request merge block/mq-deadline: Remove a WARN_ON_ONCE() call blk-mq: update hctx->dispatch_busy in case of real scheduler blk: Fix lock inversion between ioc lock and bfqd lock bfq: Remove merged request already in bfq_requests_merged() block: pass a gendisk to bdev_disk_changed block: move bdev_disk_changed block: add the events* attributes to disk_attrs block: move the disk events code to a separate file block: fix trace completion for chained bio block/partitions/msdos: Fix typo inidicator -> indicator block, bfq: reset waker pointer with shared queues block, bfq: check waker only for queues with no in-flight I/O block, bfq: avoid delayed merge of async queues block, bfq: boost throughput by extending queue-merging times block, bfq: consider also creation time in delayed stable merge block, bfq: fix delayed stable merge check block, bfq: let also stably merged queues enjoy weight raising blk-wbt: make sure throttle is enabled properly blk-wbt: introduce a new disable state to prevent false positive by rwb_enabled() ...
| * | | rq-qos: fix missed wake-ups in rq_qos_throttle try twoJan Kara2021-06-081-2/+7
| | |/ | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 545fbd0775ba ("rq-qos: fix missed wake-ups in rq_qos_throttle") tried to fix a problem that a process could be sleeping in rq_qos_wait() without anyone to wake it up. However the fix is not complete and the following can still happen: CPU1 (waiter1) CPU2 (waiter2) CPU3 (waker) rq_qos_wait() rq_qos_wait() acquire_inflight_cb() -> fails acquire_inflight_cb() -> fails completes IOs, inflight decreased prepare_to_wait_exclusive() prepare_to_wait_exclusive() has_sleeper = !wq_has_single_sleeper() -> true as there are two sleepers has_sleeper = !wq_has_single_sleeper() -> true io_schedule() io_schedule() Deadlock as now there's nobody to wakeup the two waiters. The logic automatically blocking when there are already sleepers is really subtle and the only way to make it work reliably is that we check whether there are some waiters in the queue when adding ourselves there. That way, we are guaranteed that at least the first process to enter the wait queue will recheck the waiting condition before going to sleep and thus guarantee forward progress. Fixes: 545fbd0775ba ("rq-qos: fix missed wake-ups in rq_qos_throttle") CC: stable@vger.kernel.org Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20210607112613.25344-1-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | | Merge tag 'timers-nohz-2021-06-28' of ↵Linus Torvalds2021-06-281-1/+6
|\ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timers/nohz updates from Ingo Molnar: - Micro-optimize tick_nohz_full_cpu() - Optimize idle exit tick restarts to be less eager - Optimize tick_nohz_dep_set_task() to only wake up a single CPU. This reduces IPIs and interruptions on nohz_full CPUs. - Optimize tick_nohz_dep_set_signal() in a similar fashion. - Skip IPIs in tick_nohz_kick_task() when trying to kick a non-running task. - Micro-optimize tick_nohz_task_switch() IRQ flags handling to reduce context switching costs. - Misc cleanups and fixes * tag 'timers-nohz-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: MAINTAINERS: Add myself as context tracking maintainer tick/nohz: Call tick_nohz_task_switch() with interrupts disabled tick/nohz: Kick only _queued_ task whose tick dependency is updated tick/nohz: Change signal tick dependency to wake up CPUs of member tasks tick/nohz: Only wake up a single target cpu when kicking a task tick/nohz: Update nohz_full Kconfig help tick/nohz: Update idle_exittime on actual idle exit tick/nohz: Remove superflous check for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE tick/nohz: Conditionally restart tick on idle exit tick/nohz: Evaluate the CPU expression after the static key
| * | | tick/nohz: Call tick_nohz_task_switch() with interrupts disabledPeter Zijlstra2021-05-131-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Call tick_nohz_task_switch() slightly earlier after the context switch to benefit from disabled IRQs. This way the function doesn't need to disable them once more. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20210512232924.150322-10-frederic@kernel.org
| * | | tick/nohz: Kick only _queued_ task whose tick dependency is updatedMarcelo Tosatti2021-05-131-0/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When the tick dependency of a task is updated, we want it to aknowledge the new state and restart the tick if needed. If the task is not running, we don't need to kick it because it will observe the new dependency upon scheduling in. But if the task is running, we may need to send an IPI to it so that it gets notified. Unfortunately we don't have the means to check if a task is running in a race free way. Checking p->on_cpu in a synchronized way against p->tick_dep_mask would imply adding a full barrier between prepare_task_switch() and tick_nohz_task_switch(), which we want to avoid in this fast-path. Therefore we blindly fire an IPI to the task's CPU. Meanwhile we can check if the task is queued on the CPU rq because p->on_rq is always set to TASK_ON_RQ_QUEUED _before_ schedule() and its full barrier that precedes tick_nohz_task_switch(). And if the task is queued on a nohz_full CPU, it also has fair chances to be running as the isolation constraints prescribe running single tasks on full dynticks CPUs. So use this as a trick to check if we can spare an IPI toward a non-running task. NOTE: For the ordering to be correct, it is assumed that we never deactivate a task while it is running, the only exception being the task deactivating itself while scheduling out. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20210512232924.150322-9-frederic@kernel.org
* | | | Merge tag 'sched-core-2021-06-28' of ↵Linus Torvalds2021-06-2818-514/+2174
|\ \ \ \ | | |_|/ | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler udpates from Ingo Molnar: - Changes to core scheduling facilities: - Add "Core Scheduling" via CONFIG_SCHED_CORE=y, which enables coordinated scheduling across SMT siblings. This is a much requested feature for cloud computing platforms, to allow the flexible utilization of SMT siblings, without exposing untrusted domains to information leaks & side channels, plus to ensure more deterministic computing performance on SMT systems used by heterogenous workloads. There are new prctls to set core scheduling groups, which allows more flexible management of workloads that can share siblings. - Fix task->state access anti-patterns that may result in missed wakeups and rename it to ->__state in the process to catch new abuses. - Load-balancing changes: - Tweak newidle_balance for fair-sched, to improve 'memcache'-like workloads. - "Age" (decay) average idle time, to better track & improve workloads such as 'tbench'. - Fix & improve energy-aware (EAS) balancing logic & metrics. - Fix & improve the uclamp metrics. - Fix task migration (taskset) corner case on !CONFIG_CPUSET. - Fix RT and deadline utilization tracking across policy changes - Introduce a "burstable" CFS controller via cgroups, which allows bursty CPU-bound workloads to borrow a bit against their future quota to improve overall latencies & batching. Can be tweaked via /sys/fs/cgroup/cpu/<X>/cpu.cfs_burst_us. - Rework assymetric topology/capacity detection & handling. - Scheduler statistics & tooling: - Disable delayacct by default, but add a sysctl to enable it at runtime if tooling needs it. Use static keys and other optimizations to make it more palatable. - Use sched_clock() in delayacct, instead of ktime_get_ns(). - Misc cleanups and fixes. * tag 'sched-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (72 commits) sched/doc: Update the CPU capacity asymmetry bits sched/topology: Rework CPU capacity asymmetry detection sched/core: Introduce SD_ASYM_CPUCAPACITY_FULL sched_domain flag psi: Fix race between psi_trigger_create/destroy sched/fair: Introduce the burstable CFS controller sched/uclamp: Fix uclamp_tg_restrict() sched/rt: Fix Deadline utilization tracking during policy change sched/rt: Fix RT utilization tracking during policy change sched: Change task_struct::state sched,arch: Remove unused TASK_STATE offsets sched,timer: Use __set_current_state() sched: Add get_current_state() sched,perf,kvm: Fix preemption condition sched: Introduce task_is_running() sched: Unbreak wakeups sched/fair: Age the average idle time sched/cpufreq: Consider reduced CPU capacity in energy calculation sched/fair: Take thermal pressure into account while estimating energy thermal/cpufreq_cooling: Update offline CPUs per-cpu thermal_pressure sched/fair: Return early from update_tg_cfs_load() if delta == 0 ...
| * | | sched/topology: Rework CPU capacity asymmetry detectionBeata Michalska2021-06-241-78/+131
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently the CPU capacity asymmetry detection, performed through asym_cpu_capacity_level, tries to identify the lowest topology level at which the highest CPU capacity is being observed, not necessarily finding the level at which all possible capacity values are visible to all CPUs, which might be bit problematic for some possible/valid asymmetric topologies i.e.: DIE [ ] MC [ ][ ] CPU [0] [1] [2] [3] [4] [5] [6] [7] Capacity |.....| |.....| |.....| |.....| L M B B Where: arch_scale_cpu_capacity(L) = 512 arch_scale_cpu_capacity(M) = 871 arch_scale_cpu_capacity(B) = 1024 In this particular case, the asymmetric topology level will point at MC, as all possible CPU masks for that level do cover the CPU with the highest capacity. It will work just fine for the first cluster, not so much for the second one though (consider the find_energy_efficient_cpu which might end up attempting the energy aware wake-up for a domain that does not see any asymmetry at all) Rework the way the capacity asymmetry levels are being detected, allowing to point to the lowest topology level (for a given CPU), where full set of available CPU capacities is visible to all CPUs within given domain. As a result, the per-cpu sd_asym_cpucapacity might differ across the domains. This will have an impact on EAS wake-up placement in a way that it might see different range of CPUs to be considered, depending on the given current and target CPUs. Additionally, those levels, where any range of asymmetry (not necessarily full) is being detected will get identified as well. The selected asymmetric topology level will be denoted by SD_ASYM_CPUCAPACITY_FULL sched domain flag whereas the 'sub-levels' would receive the already used SD_ASYM_CPUCAPACITY flag. This allows maintaining the current behaviour for asymmetric topologies, with misfit migration operating correctly on lower levels, if applicable, as any asymmetry is enough to trigger the misfit migration. The logic there relies on the SD_ASYM_CPUCAPACITY flag and does not relate to the full asymmetry level denoted by the sd_asym_cpucapacity pointer. Detecting the CPU capacity asymmetry is being based on a set of available CPU capacities for all possible CPUs. This data is being generated upon init and updated once CPU topology changes are being detected (through arch_update_cpu_topology). As such, any changes to identified CPU capacities (like initializing cpufreq) need to be explicitly advertised by corresponding archs to trigger rebuilding the data. Additional -dflags- parameter, used when building sched domains, has been removed as well, as the asymmetry flags are now being set directly in sd_init. Suggested-by: Peter Zijlstra <peterz@infradead.org> Suggested-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Beata Michalska <beata.michalska@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lore.kernel.org/r/20210603140627.8409-3-beata.michalska@arm.com
| * | | psi: Fix race between psi_trigger_create/destroyZhaoyang Huang2021-06-241-6/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Race detected between psi_trigger_destroy/create as shown below, which cause panic by accessing invalid psi_system->poll_wait->wait_queue_entry and psi_system->poll_timer->entry->next. Under this modification, the race window is removed by initialising poll_wait and poll_timer in group_init which are executed only once at beginning. psi_trigger_destroy() psi_trigger_create() mutex_lock(trigger_lock); rcu_assign_pointer(poll_task, NULL); mutex_unlock(trigger_lock); mutex_lock(trigger_lock); if (!rcu_access_pointer(group->poll_task)) { timer_setup(poll_timer, poll_timer_fn, 0); rcu_assign_pointer(poll_task, task); } mutex_unlock(trigger_lock); synchronize_rcu(); del_timer_sync(poll_timer); <-- poll_timer has been reinitialized by psi_trigger_create() So, trigger_lock/RCU correctly protects destruction of group->poll_task but misses this race affecting poll_timer and poll_wait. Fixes: 461daba06bdc ("psi: eliminate kthread_worker from psi trigger scheduling mechanism") Co-developed-by: ziwei.dai <ziwei.dai@unisoc.com> Signed-off-by: ziwei.dai <ziwei.dai@unisoc.com> Co-developed-by: ke.wang <ke.wang@unisoc.com> Signed-off-by: ke.wang <ke.wang@unisoc.com> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Suren Baghdasaryan <surenb@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Link: https://lkml.kernel.org/r/1623371374-15664-1-git-send-email-huangzhaoyang@gmail.com
| * | | sched/fair: Introduce the burstable CFS controllerHuaixin Chang2021-06-243-10/+73
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The CFS bandwidth controller limits CPU requests of a task group to quota during each period. However, parallel workloads might be bursty so that they get throttled even when their average utilization is under quota. And they are latency sensitive at the same time so that throttling them is undesired. We borrow time now against our future underrun, at the cost of increased interference against the other system users. All nicely bounded. Traditional (UP-EDF) bandwidth control is something like: (U = \Sum u_i) <= 1 This guaranteeds both that every deadline is met and that the system is stable. After all, if U were > 1, then for every second of walltime, we'd have to run more than a second of program time, and obviously miss our deadline, but the next deadline will be further out still, there is never time to catch up, unbounded fail. This work observes that a workload doesn't always executes the full quota; this enables one to describe u_i as a statistical distribution. For example, have u_i = {x,e}_i, where x is the p(95) and x+e p(100) (the traditional WCET). This effectively allows u to be smaller, increasing the efficiency (we can pack more tasks in the system), but at the cost of missing deadlines when all the odds line up. However, it does maintain stability, since every overrun must be paired with an underrun as long as our x is above the average. That is, suppose we have 2 tasks, both specify a p(95) value, then we have a p(95)*p(95) = 90.25% chance both tasks are within their quota and everything is good. At the same time we have a p(5)p(5) = 0.25% chance both tasks will exceed their quota at the same time (guaranteed deadline fail). Somewhere in between there's a threshold where one exceeds and the other doesn't underrun enough to compensate; this depends on the specific CDFs. At the same time, we can say that the worst case deadline miss, will be \Sum e_i; that is, there is a bounded tardiness (under the assumption that x+e is indeed WCET). The benefit of burst is seen when testing with schbench. Default value of kernel.sched_cfs_bandwidth_slice_us(5ms) and CONFIG_HZ(1000) is used. mkdir /sys/fs/cgroup/cpu/test echo $$ > /sys/fs/cgroup/cpu/test/cgroup.procs echo 100000 > /sys/fs/cgroup/cpu/test/cpu.cfs_quota_us echo 100000 > /sys/fs/cgroup/cpu/test/cpu.cfs_burst_us ./schbench -m 1 -t 3 -r 20 -c 80000 -R 10 The average CPU usage is at 80%. I run this for 10 times, and got long tail latency for 6 times and got throttled for 8 times. Tail latencies are shown below, and it wasn't the worst case. Latency percentiles (usec) 50.0000th: 19872 75.0000th: 21344 90.0000th: 22176 95.0000th: 22496 *99.0000th: 22752 99.5000th: 22752 99.9000th: 22752 min=0, max=22727 rps: 9.90 p95 (usec) 22496 p99 (usec) 22752 p95/cputime 28.12% p99/cputime 28.44% The interferenece when using burst is valued by the possibilities for missing the deadline and the average WCET. Test results showed that when there many cgroups or CPU is under utilized, the interference is limited. More details are shown in: https://lore.kernel.org/lkml/5371BD36-55AE-4F71-B9D7-B86DC32E3D2B@linux.alibaba.com/ Co-developed-by: Shanpei Chen <shanpeic@linux.alibaba.com> Signed-off-by: Shanpei Chen <shanpeic@linux.alibaba.com> Co-developed-by: Tianchen Ding <dtcccc@linux.alibaba.com> Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com> Signed-off-by: Huaixin Chang <changhuaixin@linux.alibaba.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Ben Segall <bsegall@google.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20210621092800.23714-2-changhuaixin@linux.alibaba.com
| * | | sched/uclamp: Fix uclamp_tg_restrict()Qais Yousef2021-06-221-31/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Now cpu.uclamp.min acts as a protection, we need to make sure that the uclamp request of the task is within the allowed range of the cgroup, that is it is clamp()'ed correctly by tg->uclamp[UCLAMP_MIN] and tg->uclamp[UCLAMP_MAX]. As reported by Xuewen [1] we can have some corner cases where there's inversion between uclamp requested by task (p) and the uclamp values of the taskgroup it's attached to (tg). Following table demonstrates 2 corner cases: | p | tg | effective -----------+-----+------+----------- CASE 1 -----------+-----+------+----------- uclamp_min | 60% | 0% | 60% -----------+-----+------+----------- uclamp_max | 80% | 50% | 50% -----------+-----+------+----------- CASE 2 -----------+-----+------+----------- uclamp_min | 0% | 30% | 30% -----------+-----+------+----------- uclamp_max | 20% | 50% | 20% -----------+-----+------+----------- With this fix we get: | p | tg | effective -----------+-----+------+----------- CASE 1 -----------+-----+------+----------- uclamp_min | 60% | 0% | 50% -----------+-----+------+----------- uclamp_max | 80% | 50% | 50% -----------+-----+------+----------- CASE 2 -----------+-----+------+----------- uclamp_min | 0% | 30% | 30% -----------+-----+------+----------- uclamp_max | 20% | 50% | 30% -----------+-----+------+----------- Additionally uclamp_update_active_tasks() must now unconditionally update both UCLAMP_MIN/MAX because changing the tg's UCLAMP_MAX for instance could have an impact on the effective UCLAMP_MIN of the tasks. | p | tg | effective -----------+-----+------+----------- old -----------+-----+------+----------- uclamp_min | 60% | 0% | 50% -----------+-----+------+----------- uclamp_max | 80% | 50% | 50% -----------+-----+------+----------- *new* -----------+-----+------+----------- uclamp_min | 60% | 0% | *60%* -----------+-----+------+----------- uclamp_max | 80% |*70%* | *70%* -----------+-----+------+----------- [1] https://lore.kernel.org/lkml/CAB8ipk_a6VFNjiEnHRHkUMBKbA+qzPQvhtNjJ_YNzQhqV_o8Zw@mail.gmail.com/ Fixes: 0c18f2ecfcc2 ("sched/uclamp: Fix wrong implementation of cpu.uclamp.min") Reported-by: Xuewen Yan <xuewen.yan94@gmail.com> Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210617165155.3774110-1-qais.yousef@arm.com
| * | | sched/rt: Fix Deadline utilization tracking during policy changeVincent Donnefort2021-06-221-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | DL keeps track of the utilization on a per-rq basis with the structure avg_dl. This utilization is updated during task_tick_dl(), put_prev_task_dl() and set_next_task_dl(). However, when the current running task changes its policy, set_next_task_dl() which would usually take care of updating the utilization when the rq starts running DL tasks, will not see a such change, leaving the avg_dl structure outdated. When that very same task will be dequeued later, put_prev_task_dl() will then update the utilization, based on a wrong last_update_time, leading to a huge spike in the DL utilization signal. The signal would eventually recover from this issue after few ms. Even if no DL tasks are run, avg_dl is also updated in __update_blocked_others(). But as the CPU capacity depends partly on the avg_dl, this issue has nonetheless a significant impact on the scheduler. Fix this issue by ensuring a load update when a running task changes its policy to DL. Fixes: 3727e0e ("sched/dl: Add dl_rq utilization tracking") Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/1624271872-211872-3-git-send-email-vincent.donnefort@arm.com
| * | | sched/rt: Fix RT utilization tracking during policy changeVincent Donnefort2021-06-221-5/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | RT keeps track of the utilization on a per-rq basis with the structure avg_rt. This utilization is updated during task_tick_rt(), put_prev_task_rt() and set_next_task_rt(). However, when the current running task changes its policy, set_next_task_rt() which would usually take care of updating the utilization when the rq starts running RT tasks, will not see a such change, leaving the avg_rt structure outdated. When that very same task will be dequeued later, put_prev_task_rt() will then update the utilization, based on a wrong last_update_time, leading to a huge spike in the RT utilization signal. The signal would eventually recover from this issue after few ms. Even if no RT tasks are run, avg_rt is also updated in __update_blocked_others(). But as the CPU capacity depends partly on the avg_rt, this issue has nonetheless a significant impact on the scheduler. Fix this issue by ensuring a load update when a running task changes its policy to RT. Fixes: 371bf427 ("sched/rt: Add rt_rq utilization tracking") Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/1624271872-211872-2-git-send-email-vincent.donnefort@arm.com
| * | | sched: Change task_struct::statePeter Zijlstra2021-06-183-34/+40
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Change the type and name of task_struct::state. Drop the volatile and shrink it to an 'unsigned int'. Rename it in order to find all uses such that we can use READ_ONCE/WRITE_ONCE as appropriate. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com> Acked-by: Will Deacon <will@kernel.org> Acked-by: Daniel Thompson <daniel.thompson@linaro.org> Link: https://lore.kernel.org/r/20210611082838.550736351@infradead.org
| * | | sched: Add get_current_state()Peter Zijlstra2021-06-181-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Remove yet another few p->state accesses. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20210611082838.347475156@infradead.org
| * | | sched: Introduce task_is_running()Peter Zijlstra2021-06-182-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Replace a bunch of 'p->state == TASK_RUNNING' with a new helper: task_is_running(p). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Davidlohr Bueso <dave@stgolabs.net> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20210611082838.222401495@infradead.org
| * | | Merge branch 'sched/urgent' into sched/core, to resolve conflictsIngo Molnar2021-06-183-41/+40
| |\ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit in sched/urgent moved the cfs_rq_is_decayed() function: a7b359fc6a37: ("sched/fair: Correctly insert cfs_rq's to list on unthrottle") and this fresh commit in sched/core modified it in the old location: 9e077b52d86a: ("sched/pelt: Check that *_avg are null when *_sum are") Merge the two variants. Conflicts: kernel/sched/fair.c Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched/fair: Age the average idle timePeter Zijlstra2021-06-173-4/+29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This is a partial forward-port of Peter Ziljstra's work first posted at: https://lore.kernel.org/lkml/20180530142236.667774973@infradead.org/ Currently select_idle_cpu()'s proportional scheme uses the average idle time *for when we are idle*, that is temporally challenged. When a CPU is not at all idle, we'll happily continue using whatever value we did see when the CPU goes idle. To fix this, introduce a separate average idle and age it (the existing value still makes sense for things like new-idle balancing, which happens when we do go idle). The overall goal is to not spend more time scanning for idle CPUs than we're idle for. Otherwise we're inhibiting work. This means that we need to consider the cost over all the wake-ups between consecutive idle periods. To track this, the scan cost is subtracted from the estimated average idle time. The impact of this patch is related to workloads that have domains that are fully busy or overloaded. Without the patch, the scan depth may be too high because a CPU is not reaching idle. Due to the nature of the patch, this is a regression magnet. It potentially wins when domains are almost fully busy or overloaded -- at that point searches are likely to fail but idle is not being aged as CPUs are active so search depth is too large and useless. It will potentially show regressions when there are idle CPUs and a deep search is beneficial. This tbench result on a 2-socket broadwell machine partially illustates the problem 5.13.0-rc2 5.13.0-rc2 vanilla sched-avgidle-v1r5 Hmean 1 445.02 ( 0.00%) 451.36 * 1.42%* Hmean 2 830.69 ( 0.00%) 846.03 * 1.85%* Hmean 4 1350.80 ( 0.00%) 1505.56 * 11.46%* Hmean 8 2888.88 ( 0.00%) 2586.40 * -10.47%* Hmean 16 5248.18 ( 0.00%) 5305.26 * 1.09%* Hmean 32 8914.03 ( 0.00%) 9191.35 * 3.11%* Hmean 64 10663.10 ( 0.00%) 10192.65 * -4.41%* Hmean 128 18043.89 ( 0.00%) 18478.92 * 2.41%* Hmean 256 16530.89 ( 0.00%) 17637.16 * 6.69%* Hmean 320 16451.13 ( 0.00%) 17270.97 * 4.98%* Note that 8 was a regression point where a deeper search would have helped but it gains for high thread counts when searches are useless. Hackbench is a more extreme example although not perfect as the tasks idle rapidly hackbench-process-pipes 5.13.0-rc2 5.13.0-rc2 vanilla sched-avgidle-v1r5 Amean 1 0.3950 ( 0.00%) 0.3887 ( 1.60%) Amean 4 0.9450 ( 0.00%) 0.9677 ( -2.40%) Amean 7 1.4737 ( 0.00%) 1.4890 ( -1.04%) Amean 12 2.3507 ( 0.00%) 2.3360 * 0.62%* Amean 21 4.0807 ( 0.00%) 4.0993 * -0.46%* Amean 30 5.6820 ( 0.00%) 5.7510 * -1.21%* Amean 48 8.7913 ( 0.00%) 8.7383 ( 0.60%) Amean 79 14.3880 ( 0.00%) 13.9343 * 3.15%* Amean 110 21.2233 ( 0.00%) 19.4263 * 8.47%* Amean 141 28.2930 ( 0.00%) 25.1003 * 11.28%* Amean 172 34.7570 ( 0.00%) 30.7527 * 11.52%* Amean 203 41.0083 ( 0.00%) 36.4267 * 11.17%* Amean 234 47.7133 ( 0.00%) 42.0623 * 11.84%* Amean 265 53.0353 ( 0.00%) 47.7720 * 9.92%* Amean 296 60.0170 ( 0.00%) 53.4273 * 10.98%* Stddev 1 0.0052 ( 0.00%) 0.0025 ( 51.57%) Stddev 4 0.0357 ( 0.00%) 0.0370 ( -3.75%) Stddev 7 0.0190 ( 0.00%) 0.0298 ( -56.64%) Stddev 12 0.0064 ( 0.00%) 0.0095 ( -48.38%) Stddev 21 0.0065 ( 0.00%) 0.0097 ( -49.28%) Stddev 30 0.0185 ( 0.00%) 0.0295 ( -59.54%) Stddev 48 0.0559 ( 0.00%) 0.0168 ( 69.92%) Stddev 79 0.1559 ( 0.00%) 0.0278 ( 82.17%) Stddev 110 1.1728 ( 0.00%) 0.0532 ( 95.47%) Stddev 141 0.7867 ( 0.00%) 0.0968 ( 87.69%) Stddev 172 1.0255 ( 0.00%) 0.0420 ( 95.91%) Stddev 203 0.8106 ( 0.00%) 0.1384 ( 82.92%) Stddev 234 1.1949 ( 0.00%) 0.1328 ( 88.89%) Stddev 265 0.9231 ( 0.00%) 0.0820 ( 91.11%) Stddev 296 1.0456 ( 0.00%) 0.1327 ( 87.31%) Again, higher thread counts benefit and the standard deviation shows that results are also a lot more stable when the idle time is aged. The patch potentially matters when a socket was multiple LLCs as the maximum search depth is lower. However, some of the test results were suspiciously good (e.g. specjbb2005 gaining 50% on a Zen1 machine) and other results were not dramatically different to other mcahines. Given the nature of the patch, Peter's full series is not being forward ported as each part should stand on its own. Preferably they would be merged at different times to reduce the risk of false bisections. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210615111611.GH30378@techsingularity.net
| * | | | sched/cpufreq: Consider reduced CPU capacity in energy calculationLukasz Luba2021-06-172-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Energy Aware Scheduling (EAS) needs to predict the decisions made by SchedUtil. The map_util_freq() exists to do that. There are corner cases where the max allowed frequency might be reduced (due to thermal). SchedUtil as a CPUFreq governor, is aware of that but EAS is not. This patch aims to address it. SchedUtil stores the maximum allowed frequency in 'sugov_policy::next_freq' field. EAS has to predict that value, which is the real used frequency. That value is made after a call to cpufreq_driver_resolve_freq() which clamps to the CPUFreq policy limits. In the existing code EAS is not able to predict that real frequency. This leads to energy estimation errors. To avoid wrong energy estimation in EAS (due to frequency miss prediction) make sure that the step which calculates Performance Domain frequency, is also aware of the allowed CPU capacity. Furthermore, modify map_util_freq() to not extend the frequency value. Instead, use map_util_perf() to extend the util value in both places: SchedUtil and EAS, but for EAS clamp it to max allowed CPU capacity. In the end, we achieve the same desirable behavior for both subsystems and alignment in regards to the real CPU frequency. Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> (For the schedutil part) Link: https://lore.kernel.org/r/20210614191238.23224-1-lukasz.luba@arm.com
| * | | | sched/fair: Take thermal pressure into account while estimating energyLukasz Luba2021-06-171-3/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Energy Aware Scheduling (EAS) needs to be able to predict the frequency requests made by the SchedUtil governor to properly estimate energy used in the future. It has to take into account CPUs utilization and forecast Performance Domain (PD) frequency. There is a corner case when the max allowed frequency might be reduced due to thermal. SchedUtil is aware of that reduced frequency, so it should be taken into account also in EAS estimations. SchedUtil, as a CPUFreq governor, knows the maximum allowed frequency of a CPU, thanks to cpufreq_driver_resolve_freq() and internal clamping to 'policy::max'. SchedUtil is responsible to respect that upper limit while setting the frequency through CPUFreq drivers. This effective frequency is stored internally in 'sugov_policy::next_freq' and EAS has to predict that value. In the existing code the raw value of arch_scale_cpu_capacity() is used for clamping the returned CPU utilization from effective_cpu_util(). This patch fixes issue with too big single CPU utilization, by introducing clamping to the allowed CPU capacity. The allowed CPU capacity is a CPU capacity reduced by thermal pressure raw value. Thanks to knowledge about allowed CPU capacity, we don't get too big value for a single CPU utilization, which is then added to the util sum. The util sum is used as a source of information for estimating whole PD energy. To avoid wrong energy estimation in EAS (due to capped frequency), make sure that the calculation of util sum is aware of allowed CPU capacity. This thermal pressure might be visible in scenarios where the CPUs are not heavily loaded, but some other component (like GPU) drastically reduced available power budget and increased the SoC temperature. Thus, we still use EAS for task placement and CPUs are not over-utilized. Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20210614191128.22735-1-lukasz.luba@arm.com
| * | | | sched/fair: Return early from update_tg_cfs_load() if delta == 0Dietmar Eggemann2021-06-171-1/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In case the _avg delta is 0 there is no need to update se's _avg (level n) nor cfs_rq's _avg (level n-1). These values stay the same. Since cfs_rq's _avg isn't changed, i.e. no load is propagated down, cfs_rq's _sum should stay the same as well. So bail out after se's _sum has been updated. Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/20210601083616.804229-1-dietmar.eggemann@arm.com
| * | | | sched/pelt: Check that *_avg are null when *_sum areVincent Guittot2021-06-171-0/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Check that we never break the rule that pelt's avg values are null if pelt's sum are. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Acked-by: Odin Ugedal <odin@uged.al> Link: https://lore.kernel.org/r/20210601155328.19487-1-vincent.guittot@linaro.org
| * | | | sched/debug: Remove obsolete init_schedstats()Eric Dumazet2021-06-041-17/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Revert commit 4698f88c06b8 ("sched/debug: Fix 'schedstats=enable' cmdline option"). After commit 6041186a3258 ("init: initialize jump labels before command line option parsing") we can rely on jump label infra being ready for use when setup_schedstats() is called. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lkml.kernel.org/r/20210602112108.1709635-1-eric.dumazet@gmail.com
| * | | | Merge branch 'sched/urgent' into sched/core, to pick up fixesIngo Molnar2021-06-031-9/+14
| |\ \ \ \ | | | | | | | | | | | | | | | | | | Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | | sched: Don't defer CPU pick to migration_cpu_stop()Valentin Schneider2021-06-011-8/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Will reported that the 'XXX __migrate_task() can fail' in migration_cpu_stop() can happen, and it *is* sort of a big deal. Looking at it some more, one will note there is a glaring hole in the deferred CPU selection: (w/ CONFIG_CPUSET=n, so that the affinity mask passed via taskset doesn't get AND'd with cpu_online_mask) $ taskset -pc 0-2 $PID # offline CPUs 3-4 $ taskset -pc 3-5 $PID `\ $PID may stay on 0-2 due to the cpumask_any_distribute() picking an offline CPU and __migrate_task() refusing to do anything due to cpu_is_allowed(). set_cpus_allowed_ptr() goes to some length to pick a dest_cpu that matches the right constraints vs affinity and the online/active state of the CPUs. Reuse that instead of discarding it in the affine_move_task() case. Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()") Reported-by: Will Deacon <will@kernel.org> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210526205751.842360-2-valentin.schneider@arm.com
| * | | | | sched/fair: Fix ascii art by relpacing tabsOdin Ugedal2021-06-011-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When using something other than 8 spaces per tab, this ascii art makes not sense, and the reader might end up wondering what this advanced equation "is". Signed-off-by: Odin Ugedal <odin@uged.al> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lkml.kernel.org/r/20210518125202.78658-4-odin@uged.al
| * | | | | sched,init: Fix DEBUG_PREEMPT vs early bootPeter Zijlstra2021-06-011-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Extend 8fb12156b8db ("init: Pin init task to the boot CPU, initially") to cover the new PF_NO_SETAFFINITY requirement. While there, move wait_for_completion(&kthreadd_done) into kernel_init() to make it absolutely clear it is the very first thing done by the init thread. Fixes: 570a752b7a9b ("lib/smp_processor_id: Use is_percpu_thread() instead of nr_cpus_allowed") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Tested-by: Valentin Schneider <valentin.schneider@arm.com> Tested-by: Borislav Petkov <bp@alien8.de> Link: https://lkml.kernel.org/r/YLS4mbKUrA3Gnb4t@hirez.programming.kicks-ass.net
| * | | | | sched: Fix a stale comment in pick_next_task()Masahiro Yamada2021-05-191-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | fair_sched_class->next no longer exists since commit: a87e749e8fa1 ("sched: Remove struct sched_class::next field"). Now the sched_class order is specified by the linker script. Rewrite the comment in a more generic way. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20210519063709.323162-1-masahiroy@kernel.org
| * | | | | sched/uclamp: Fix locking around cpu_util_update_eff()Qais Yousef2021-05-191-0/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cpu_cgroup_css_online() calls cpu_util_update_eff() without holding the uclamp_mutex or rcu_read_lock() like other call sites, which is a mistake. The uclamp_mutex is required to protect against concurrent reads and writes that could update the cgroup hierarchy. The rcu_read_lock() is required to traverse the cgroup data structures in cpu_util_update_eff(). Surround the caller with the required locks and add some asserts to better document the dependency in cpu_util_update_eff(). Fixes: 7226017ad37a ("sched/uclamp: Fix a bug in propagating uclamp value in new cgroups") Reported-by: Quentin Perret <qperret@google.com> Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210510145032.1934078-3-qais.yousef@arm.com
| * | | | | sched/uclamp: Fix wrong implementation of cpu.uclamp.minQais Yousef2021-05-191-4/+17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cpu.uclamp.min is a protection as described in cgroup-v2 Resource Distribution Model Documentation/admin-guide/cgroup-v2.rst which means we try our best to preserve the minimum performance point of tasks in this group. See full description of cpu.uclamp.min in the cgroup-v2.rst. But the current implementation makes it a limit, which is not what was intended. For example: tg->cpu.uclamp.min = 20% p0->uclamp[UCLAMP_MIN] = 0 p1->uclamp[UCLAMP_MIN] = 50% Previous Behavior (limit): p0->effective_uclamp = 0 p1->effective_uclamp = 20% New Behavior (Protection): p0->effective_uclamp = 20% p1->effective_uclamp = 50% Which is inline with how protections should work. With this change the cgroup and per-task behaviors are the same, as expected. Additionally, we remove the confusing relationship between cgroup and !user_defined flag. We don't want for example RT tasks that are boosted by default to max to change their boost value when they attach to a cgroup. If a cgroup wants to limit the max performance point of tasks attached to it, then cpu.uclamp.max must be set accordingly. Or if they want to set different boost value based on cgroup, then sysctl_sched_util_clamp_min_rt_default must be used to NOT boost to max and set the right cpu.uclamp.min for each group to let the RT tasks obtain the desired boost value when attached to that group. As it stands the dependency on !user_defined flag adds an extra layer of complexity that is not required now cpu.uclamp.min behaves properly as a protection. The propagation model of effective cpu.uclamp.min in child cgroups as implemented by cpu_util_update_eff() is still correct. The parent protection sets an upper limit of what the child cgroups will effectively get. Fixes: 3eac870a3247 (sched/uclamp: Use TG's clamps to restrict TASK's clamps) Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210510145032.1934078-2-qais.yousef@arm.com
| * | | | | sched: Make the idle task quack like a per-CPU kthreadValentin Schneider2021-05-181-6/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | For all intents and purposes, the idle task is a per-CPU kthread. It isn't created via the same route as other pcpu kthreads however, and as a result it is missing a few bells and whistles: it fails kthread_is_per_cpu() and it doesn't have PF_NO_SETAFFINITY set. Fix the former by giving the idle task a kthread struct along with the KTHREAD_IS_PER_CPU flag. This requires some extra iffery as init_idle() call be called more than once on the same idle task. Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210510151024.2448573-2-valentin.schneider@arm.com
| * | | | | sched,stats: Further simplify sched_infoPeter Zijlstra2021-05-181-9/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There's no point doing delta==0 updates. Suggested-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
generated by cgit v1.2.3-71-gd317 (git 2.46.0) at 2026-02-02 21:56:46 +0000