tracex3_kern.c (2129B)
1/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com 2 * 3 * This program is free software; you can redistribute it and/or 4 * modify it under the terms of version 2 of the GNU General Public 5 * License as published by the Free Software Foundation. 6 */ 7#include <linux/skbuff.h> 8#include <linux/netdevice.h> 9#include <linux/version.h> 10#include <uapi/linux/bpf.h> 11#include <bpf/bpf_helpers.h> 12#include <bpf/bpf_tracing.h> 13 14struct { 15 __uint(type, BPF_MAP_TYPE_HASH); 16 __type(key, long); 17 __type(value, u64); 18 __uint(max_entries, 4096); 19} my_map SEC(".maps"); 20 21/* kprobe is NOT a stable ABI. If kernel internals change this bpf+kprobe 22 * example will no longer be meaningful 23 */ 24SEC("kprobe/blk_mq_start_request") 25int bpf_prog1(struct pt_regs *ctx) 26{ 27 long rq = PT_REGS_PARM1(ctx); 28 u64 val = bpf_ktime_get_ns(); 29 30 bpf_map_update_elem(&my_map, &rq, &val, BPF_ANY); 31 return 0; 32} 33 34static unsigned int log2l(unsigned long long n) 35{ 36#define S(k) if (n >= (1ull << k)) { i += k; n >>= k; } 37 int i = -(n == 0); 38 S(32); S(16); S(8); S(4); S(2); S(1); 39 return i; 40#undef S 41} 42 43#define SLOTS 100 44 45struct { 46 __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY); 47 __uint(key_size, sizeof(u32)); 48 __uint(value_size, sizeof(u64)); 49 __uint(max_entries, SLOTS); 50} lat_map SEC(".maps"); 51 52SEC("kprobe/blk_account_io_done") 53int bpf_prog2(struct pt_regs *ctx) 54{ 55 long rq = PT_REGS_PARM1(ctx); 56 u64 *value, l, base; 57 u32 index; 58 59 value = bpf_map_lookup_elem(&my_map, &rq); 60 if (!value) 61 return 0; 62 63 u64 cur_time = bpf_ktime_get_ns(); 64 u64 delta = cur_time - *value; 65 66 bpf_map_delete_elem(&my_map, &rq); 67 68 /* the lines below are computing index = log10(delta)*10 69 * using integer arithmetic 70 * index = 29 ~ 1 usec 71 * index = 59 ~ 1 msec 72 * index = 89 ~ 1 sec 73 * index = 99 ~ 10sec or more 74 * log10(x)*10 = log2(x)*10/log2(10) = log2(x)*3 75 */ 76 l = log2l(delta); 77 base = 1ll << l; 78 index = (l * 64 + (delta - base) * 64 / base) * 3 / 64; 79 80 if (index >= SLOTS) 81 index = SLOTS - 1; 82 83 value = bpf_map_lookup_elem(&lat_map, &index); 84 if (value) 85 *value += 1; 86 87 return 0; 88} 89char _license[] SEC("license") = "GPL"; 90u32 _version SEC("version") = LINUX_VERSION_CODE;