projects / thirdparty / man-pages.git / blame
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1 | .\" Copyright (C) 1994, 1995, Daniel Quinlan <quinlan@yggdrasil.com> |
| 2 | .\" Copyright (C) 2002-2008, 2017, Michael Kerrisk <mtk.manpages@gmail.com> | |
| 3 | .\" Copyright (C) 2023, Alejandro Colomar <alx@kernel.org> | |
| 4 | .\" | |
| 5 | .\" SPDX-License-Identifier: GPL-3.0-or-later | |
| 6 | .\" | |
| 7 | .TH proc_timer_stats 5 (date) "Linux man-pages (unreleased)" | |
| 8 | .SH NAME | |
| 9 | /proc/timer_stats \- timer statistics | |
| 10 | .SH DESCRIPTION | |
| 11 | .TP | |
| 12 | .IR /proc/timer_stats " (from Linux 2.6.21 until Linux 4.10)" | |
| 13 | .\" commit 82f67cd9fca8c8762c15ba7ed0d5747588c1e221 | |
| 14 | .\" Date: Fri Feb 16 01:28:13 2007 -0800 | |
| 15 | .\" Text largely derived from Documentation/timers/timer_stats.txt | |
| 16 | .\" removed in commit dfb4357da6ddbdf57d583ba64361c9d792b0e0b1 | |
| 17 | .\" Date: Wed Feb 8 11:26:59 2017 -0800 | |
| 18 | This is a debugging facility to make timer (ab)use in a Linux | |
| 19 | system visible to kernel and user-space developers. | |
| 20 | It can be used by kernel and user-space developers to verify that | |
| 21 | their code does not make undue use of timers. | |
| 22 | The goal is to avoid unnecessary wakeups, | |
| 23 | thereby optimizing power consumption. | |
| 24 | .IP | |
| 25 | If enabled in the kernel | |
| 26 | .RB ( CONFIG_TIMER_STATS ), | |
| 27 | but not used, | |
| 28 | it has almost zero run-time overhead and a relatively small | |
| 29 | data-structure overhead. | |
| 30 | Even if collection is enabled at run time, overhead is low: | |
| 31 | all the locking is per-CPU and lookup is hashed. | |
| 32 | .IP | |
| 33 | The | |
| 34 | .I /proc/timer_stats | |
| 35 | file is used both to control sampling facility and to read out the | |
| 36 | sampled information. | |
| 37 | .IP | |
| 38 | The | |
| 39 | .I timer_stats | |
| 40 | functionality is inactive on bootup. | |
| 41 | A sampling period can be started using the following command: | |
| 42 | .IP | |
| 43 | .in +4n | |
| 44 | .EX | |
| 45 | # echo 1 > /proc/timer_stats | |
| 46 | .EE | |
| 47 | .in | |
| 48 | .IP | |
| 49 | The following command stops a sampling period: | |
| 50 | .IP | |
| 51 | .in +4n | |
| 52 | .EX | |
| 53 | # echo 0 > /proc/timer_stats | |
| 54 | .EE | |
| 55 | .in | |
| 56 | .IP | |
| 57 | The statistics can be retrieved by: | |
| 58 | .IP | |
| 59 | .in +4n | |
| 60 | .EX | |
| 61 | $ cat /proc/timer_stats | |
| 62 | .EE | |
| 63 | .in | |
| 64 | .IP | |
| 65 | While sampling is enabled, each readout from | |
| 66 | .I /proc/timer_stats | |
| 67 | will see | |
| 68 | newly updated statistics. | |
| 69 | Once sampling is disabled, the sampled information | |
| 70 | is kept until a new sample period is started. | |
| 71 | This allows multiple readouts. | |
| 72 | .IP | |
| 73 | Sample output from | |
| 74 | .IR /proc/timer_stats : | |
| 75 | .IP | |
| 76 | .in +4n | |
| 77 | .EX | |
| 78 | .RB $ " cat /proc/timer_stats" | |
| 79 | Timer Stats Version: v0.3 | |
| 80 | Sample period: 1.764 s | |
| 81 | Collection: active | |
| 82 | 255, 0 swapper/3 hrtimer_start_range_ns (tick_sched_timer) | |
| 83 | 71, 0 swapper/1 hrtimer_start_range_ns (tick_sched_timer) | |
| 84 | 58, 0 swapper/0 hrtimer_start_range_ns (tick_sched_timer) | |
| 85 | 4, 1694 gnome\-shell mod_delayed_work_on (delayed_work_timer_fn) | |
| 86 | 17, 7 rcu_sched rcu_gp_kthread (process_timeout) | |
| 87 | \&... | |
| 88 | 1, 4911 kworker/u16:0 mod_delayed_work_on (delayed_work_timer_fn) | |
| 89 | 1D, 2522 kworker/0:0 queue_delayed_work_on (delayed_work_timer_fn) | |
| 90 | 1029 total events, 583.333 events/sec | |
| 91 | .EE | |
| 92 | .in | |
| 93 | .IP | |
| 94 | The output columns are: | |
| 95 | .RS | |
| 96 | .IP [1] 5 | |
| 97 | a count of the number of events, | |
| 98 | optionally (since Linux 2.6.23) followed by the letter \[aq]D\[aq] | |
| 99 | .\" commit c5c061b8f9726bc2c25e19dec227933a13d1e6b7 deferrable timers | |
| 100 | if this is a deferrable timer; | |
| 101 | .IP [2] | |
| 102 | the PID of the process that initialized the timer; | |
| 103 | .IP [3] | |
| 104 | the name of the process that initialized the timer; | |
| 105 | .IP [4] | |
| 106 | the function where the timer was initialized; and | |
| 107 | (in parentheses) | |
| 108 | the callback function that is associated with the timer. | |
| 109 | .RE | |
| 110 | .IP | |
| 111 | During the Linux 4.11 development cycle, | |
| 112 | this file was removed because of security concerns, | |
| 113 | as it exposes information across namespaces. | |
| 114 | Furthermore, it is possible to obtain | |
| 115 | the same information via in-kernel tracing facilities such as ftrace. | |
| 116 | .SH SEE ALSO | |
| 117 | .BR proc (5) |