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 | |