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 "vmlinux.h" 8 #include <linux/version.h> 9 #include <bpf/bpf_helpers.h> 10 #include <bpf/bpf_tracing.h> 11 12 struct start_key { 13 dev_t dev; 14 u32 _pad; 15 sector_t sector; 16 }; 17 18 struct { 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 */ 26 SEC("tracepoint/block/block_io_start") 27 int 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->sector 33 }; 34 35 bpf_map_update_elem(&my_map, &key, &val, BPF_ANY); 36 return 0; 37 } 38 39 static 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 S 46 } 47 48 #define SLOTS 100 49 50 struct { 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 */ 58 SEC("tracepoint/block/block_io_done") 59 int bpf_prog2(struct trace_event_raw_block_rq *ctx) 60 { 61 struct start_key key = { 62 .dev = ctx->dev, 63 .sector = ctx->sector 64 }; 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)*10 79 * using integer arithmetic 80 * index = 29 ~ 1 usec 81 * index = 59 ~ 1 msec 82 * index = 89 ~ 1 sec 83 * index = 99 ~ 10sec or more 84 * log10(x)*10 = log2(x)*10/log2(10) = log2(x)*3 85 */ 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 } 99 char _license[] SEC("license") = "GPL"; 100 u32 _version SEC("version") = LINUX_VERSION_CODE; 101