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1/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com2 *3 * This program is free software; you can redistribute it and/or4 * modify it under the terms of version 2 of the GNU General Public5 * License as published by the Free Software Foundation.6 */7#include "vmlinux.h"8#include <linux/version.h>9#include <bpf/bpf_helpers.h>10#include <bpf/bpf_tracing.h>11 12struct start_key {13 dev_t dev;14 u32 _pad;15 sector_t sector;16};17 18struct {19 __uint(type, BPF_MAP_TYPE_HASH);20 __type(key, long);21 __type(value, u64);22 __uint(max_entries, 4096);23} my_map SEC(".maps");24 25/* from /sys/kernel/tracing/events/block/block_io_start/format */26SEC("tracepoint/block/block_io_start")27int bpf_prog1(struct trace_event_raw_block_rq *ctx)28{29 u64 val = bpf_ktime_get_ns();30 struct start_key key = {31 .dev = ctx->dev,32 .sector = ctx->sector33 };34 35 bpf_map_update_elem(&my_map, &key, &val, BPF_ANY);36 return 0;37}38 39static unsigned int log2l(unsigned long long n)40{41#define S(k) if (n >= (1ull << k)) { i += k; n >>= k; }42 int i = -(n == 0);43 S(32); S(16); S(8); S(4); S(2); S(1);44 return i;45#undef S46}47 48#define SLOTS 10049 50struct {51 __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);52 __uint(key_size, sizeof(u32));53 __uint(value_size, sizeof(u64));54 __uint(max_entries, SLOTS);55} lat_map SEC(".maps");56 57/* from /sys/kernel/tracing/events/block/block_io_done/format */58SEC("tracepoint/block/block_io_done")59int bpf_prog2(struct trace_event_raw_block_rq *ctx)60{61 struct start_key key = {62 .dev = ctx->dev,63 .sector = ctx->sector64 };65 66 u64 *value, l, base;67 u32 index;68 69 value = bpf_map_lookup_elem(&my_map, &key);70 if (!value)71 return 0;72 73 u64 cur_time = bpf_ktime_get_ns();74 u64 delta = cur_time - *value;75 76 bpf_map_delete_elem(&my_map, &key);77 78 /* the lines below are computing index = log10(delta)*1079 * using integer arithmetic80 * index = 29 ~ 1 usec81 * index = 59 ~ 1 msec82 * index = 89 ~ 1 sec83 * index = 99 ~ 10sec or more84 * log10(x)*10 = log2(x)*10/log2(10) = log2(x)*385 */86 l = log2l(delta);87 base = 1ll << l;88 index = (l * 64 + (delta - base) * 64 / base) * 3 / 64;89 90 if (index >= SLOTS)91 index = SLOTS - 1;92 93 value = bpf_map_lookup_elem(&lat_map, &index);94 if (value)95 *value += 1;96 97 return 0;98}99char _license[] SEC("license") = "GPL";100u32 _version SEC("version") = LINUX_VERSION_CODE;101