Home » Mailing list archives » linux-kernel » 2008 » January » 23

[PATCH 18/20 -v5] mcount tracer for wakeup latency timings.

Previous thread: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled by Steven Rostedt on Wednesday, January 23, 2008 - 12:02 pm. (19 messages)

Next thread: [RFC] Userspace tracing memory mappings by Mathieu Desnoyers on Wednesday, January 23, 2008 - 12:04 pm. (5 messages)
[view original message]
From: Steven Rostedt <rostedt@...>
To: LKML <linux-kernel@...>
Cc: Ingo Molnar <mingo@...>, Linus Torvalds <torvalds@...>, Andrew Morton <akpm@...>, Peter Zijlstra <a.p.zijlstra@...>, Christoph Hellwig <hch@...>, Mathieu Desnoyers <mathieu.desnoyers@...>, Gregory Haskins <ghaskins@...>, Arnaldo Carvalho de Melo <acme@...>, Thomas Gleixner <tglx@...>, Tim Bird <tim.bird@...>, Sam Ravnborg <sam@...>, Frank Ch. Eigler <fche@...>, Jan Kiszka <jan.kiszka@...>, John Stultz <johnstul@...>, Arjan van de Ven <arjan@...>, Steven Rostedt <srostedt@...>
Subject: [PATCH 18/20 -v5] mcount tracer for wakeup latency timings.
Date: Wednesday, January 23, 2008 - 12:02 pm

This patch adds hooks to trace the wake up latency of the highest

priority waking task.


  "wakeup" is added to /debugfs/tracing/available_tracers


Also added to /debugfs/tracing


  tracing_max_latency

     holds the current max latency for the wakeup


  wakeup_thresh

     if set to other than zero, a log will be recorded

     for every wakeup that takes longer than the number

     entered in here (usecs for all counters)

     (deletes previous trace)


Examples:


  (with mcount_enabled = 0)


============

preemption latency trace v1.1.5 on 2.6.24-rc8

--------------------------------------------------------------------

 latency: 26 us, #2/2, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)

    -----------------

    | task: migration/0-3 (uid:0 nice:-5 policy:1 rt_prio:99)

    -----------------


                 _------=> CPU#

                / _-----=> irqs-off

               | / _----=> need-resched

               || / _---=> hardirq/softirq

               ||| / _--=> preempt-depth

               |||| /

               |||||     delay

   cmd     pid ||||| time  |   caller

      \   /    |||||   \   |   /

   quilt-8551  0d..3    0us+: wake_up_process+0x15/0x17 <ffffffff80233e80> (sched_exec+0xc9/0x100 <ffffffff80235343>)

   quilt-8551  0d..4   26us : sched_switch_callback+0x73/0x81 <ffffffff80338d2f> (schedule+0x483/0x6d5 <ffffffff8048b3ee>)


vim:ft=help

============


  (with mcount_enabled = 1)


============

preemption latency trace v1.1.5 on 2.6.24-rc8

--------------------------------------------------------------------

 latency: 36 us, #45/45, CPU#0 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)

    -----------------

    | task: migration/1-5 (uid:0 nice:-5 policy:1 rt_prio:99)

    -----------------


                 _------=> CPU#

                / _-----=> irqs-off

               | / _----=> need-resched

            ...
[ message continues ]
Previous thread: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled by Steven Rostedt on Wednesday, January 23, 2008 - 12:02 pm. (19 messages)

Next thread: [RFC] Userspace tracing memory mappings by Mathieu Desnoyers on Wednesday, January 23, 2008 - 12:04 pm. (5 messages)