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 | |
Brendan Gregg | f92e668 | 2015-09-10 11:34:28 -0700 | [diff] [blame^] | 16 | BPF_HASH(start, u32); |
Brendan Gregg | 48fbc3e | 2015-08-18 14:56:14 -0700 | [diff] [blame] | 17 | BPF_TABLE("array", int, u64, dist, 64); |
| 18 | |
| 19 | static unsigned int log2(unsigned int v) |
| 20 | { |
| 21 | unsigned int r; |
| 22 | unsigned int shift; |
| 23 | |
| 24 | r = (v > 0xFFFF) << 4; v >>= r; |
| 25 | shift = (v > 0xFF) << 3; v >>= shift; r |= shift; |
| 26 | shift = (v > 0xF) << 2; v >>= shift; r |= shift; |
| 27 | shift = (v > 0x3) << 1; v >>= shift; r |= shift; |
| 28 | r |= (v >> 1); |
| 29 | return r; |
| 30 | } |
| 31 | |
| 32 | static unsigned int log2l(unsigned long v) |
| 33 | { |
| 34 | unsigned int hi = v >> 32; |
| 35 | if (hi) |
| 36 | return log2(hi) + 32 + 1; |
| 37 | else |
| 38 | return log2(v) + 1; |
| 39 | } |
| 40 | |
| 41 | int do_entry(struct pt_regs *ctx) |
| 42 | { |
Brendan Gregg | f92e668 | 2015-09-10 11:34:28 -0700 | [diff] [blame^] | 43 | u32 pid; |
Brendan Gregg | 48fbc3e | 2015-08-18 14:56:14 -0700 | [diff] [blame] | 44 | u64 ts, *val, zero = 0; |
| 45 | |
Brendan Gregg | f92e668 | 2015-09-10 11:34:28 -0700 | [diff] [blame^] | 46 | pid = bpf_get_current_pid_tgid(); |
Brendan Gregg | 48fbc3e | 2015-08-18 14:56:14 -0700 | [diff] [blame] | 47 | ts = bpf_ktime_get_ns(); |
Brendan Gregg | f92e668 | 2015-09-10 11:34:28 -0700 | [diff] [blame^] | 48 | start.update(&pid, &ts); |
Brendan Gregg | 48fbc3e | 2015-08-18 14:56:14 -0700 | [diff] [blame] | 49 | return 0; |
| 50 | } |
| 51 | |
| 52 | int do_return(struct pt_regs *ctx) |
| 53 | { |
Brendan Gregg | f92e668 | 2015-09-10 11:34:28 -0700 | [diff] [blame^] | 54 | u32 pid; |
Brendan Gregg | 48fbc3e | 2015-08-18 14:56:14 -0700 | [diff] [blame] | 55 | u64 *tsp, delta; |
| 56 | |
Brendan Gregg | f92e668 | 2015-09-10 11:34:28 -0700 | [diff] [blame^] | 57 | pid = bpf_get_current_pid_tgid(); |
| 58 | tsp = start.lookup(&pid); |
Brendan Gregg | 48fbc3e | 2015-08-18 14:56:14 -0700 | [diff] [blame] | 59 | |
| 60 | if (tsp != 0) { |
| 61 | delta = bpf_ktime_get_ns() - *tsp; |
| 62 | int index = log2l(delta / 1000); |
| 63 | u64 *leaf = dist.lookup(&index); |
| 64 | if (leaf) (*leaf)++; |
Brendan Gregg | f92e668 | 2015-09-10 11:34:28 -0700 | [diff] [blame^] | 65 | start.delete(&pid); |
Brendan Gregg | 48fbc3e | 2015-08-18 14:56:14 -0700 | [diff] [blame] | 66 | } |
| 67 | |
| 68 | return 0; |
| 69 | } |