[linux-audio-dev] [PATCH] latency-profiling for 2.4.0-test3-pre2

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Subject: [linux-audio-dev] [PATCH] latency-profiling for 2.4.0-test3-pre2
From: Roger Larsson (roger.larsson_AT_norran.net)
Date: Mon Jul 03 2000 - 20:17:00 EEST

Hi all,

Since there has been much talk about latencies lately I updated my
latency profiling patch to the most recent kernel.

Note: I have simplified usage.

Output format (changed):

  Latency <dt>ms PID <pid> % <name>
  Trace; [<IP>] [<IP>]

  dt
         latency time from rescheduling request (need_resched = 1) until
actually done.
  pid
         process id
  IPs
         instruction pointers, decode as any (sampled!) kernel stack
trace.
         Note: there might be none since they are sampled with HZ
  name
         the running process name. But the problem really is inside the
kernel. A process
         running in user space would have been (un-)scheduled
immediately!!!

Example (output from dmesg):
  Latency 708ms PID 267 % modprobe
  Trace: [<c0205d7e>] [<c0205d7e>] [<c0205d7e>] [<c0205d7e>]
[<c0205d7e>]
  [<c0205d7e>] [<c0205d7e>] [<c0205d80>] [<c0205d7e>] [<c0205d7e>]

With the modified format you may get symbols by:
  dmesg | ksymoops

Trace: c0205d7e <__rdtsc_delay+e/18>
Trace: c0205d7e <__rdtsc_delay+e/18>
Trace: c0205d7e <__rdtsc_delay+e/18>
Trace: c0205d7e <__rdtsc_delay+e/18>
Trace: c0205d7e <__rdtsc_delay+e/18>
Trace: c0205d7e <__rdtsc_delay+e/18>
Trace: c0205d7e <__rdtsc_delay+e/18>
Trace: c0205d80 <__rdtsc_delay+10/18>
Trace: c0205d7e <__rdtsc_delay+e/18>
Trace: c0205d7e <__rdtsc_delay+e/18>
 
But again, note that this is NOT a stack trace. The trace is in sample
order with HZ (10 ms) run time in between.

/RogerL 

--
Home page:
  http://www.norran.net/nra02596/
latency-profiling-2.4.0-test3-r9.patch

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