Brendan Gregg | 48fbc3e | 2015-08-18 14:56:14 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * vfsreadlat.c VFS read latency distribution. |
| 3 | * For Linux, uses BCC, eBPF. See .py file. |
| 4 | * |
| 5 | * Based on eBPF sample tracex2 by Alexi Starovoitov. |
| 6 | * Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com |
| 7 | * This program is free software; you can redistribute it and/or |
| 8 | * modify it under the terms of version 2 of the GNU General Public |
| 9 | * License as published by the Free Software Foundation. |
| 10 | * |
| 11 | * 15-Aug-2015 Brendan Gregg Created this. |
| 12 | */ |
| 13 | |
| 14 | #include <uapi/linux/ptrace.h> |
| 15 | |
| 16 | struct key_t { |
| 17 | u32 pid; |
| 18 | }; |
| 19 | |
| 20 | BPF_TABLE("hash", struct key_t, u64, start, 10240); |
| 21 | BPF_TABLE("array", int, u64, dist, 64); |
| 22 | |
| 23 | static unsigned int log2(unsigned int v) |
| 24 | { |
| 25 | unsigned int r; |
| 26 | unsigned int shift; |
| 27 | |
| 28 | r = (v > 0xFFFF) << 4; v >>= r; |
| 29 | shift = (v > 0xFF) << 3; v >>= shift; r |= shift; |
| 30 | shift = (v > 0xF) << 2; v >>= shift; r |= shift; |
| 31 | shift = (v > 0x3) << 1; v >>= shift; r |= shift; |
| 32 | r |= (v >> 1); |
| 33 | return r; |
| 34 | } |
| 35 | |
| 36 | static unsigned int log2l(unsigned long v) |
| 37 | { |
| 38 | unsigned int hi = v >> 32; |
| 39 | if (hi) |
| 40 | return log2(hi) + 32 + 1; |
| 41 | else |
| 42 | return log2(v) + 1; |
| 43 | } |
| 44 | |
| 45 | int do_entry(struct pt_regs *ctx) |
| 46 | { |
| 47 | struct key_t key = {}; |
| 48 | u64 ts, *val, zero = 0; |
| 49 | |
| 50 | key.pid = bpf_get_current_pid_tgid(); |
| 51 | ts = bpf_ktime_get_ns(); |
| 52 | start.update(&key, &ts); |
| 53 | return 0; |
| 54 | } |
| 55 | |
| 56 | int do_return(struct pt_regs *ctx) |
| 57 | { |
| 58 | struct key_t key = {}; |
| 59 | u64 *tsp, delta; |
| 60 | |
| 61 | key.pid = bpf_get_current_pid_tgid(); |
| 62 | tsp = start.lookup(&key); |
| 63 | |
| 64 | if (tsp != 0) { |
| 65 | delta = bpf_ktime_get_ns() - *tsp; |
| 66 | int index = log2l(delta / 1000); |
| 67 | u64 *leaf = dist.lookup(&index); |
| 68 | if (leaf) (*leaf)++; |
| 69 | start.delete(&key); |
| 70 | } |
| 71 | |
| 72 | return 0; |
| 73 | } |