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SubjectRe: [patch] voluntary-preempt-2.6.9-rc1-bk12-R5
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On Sun, 2004-09-05 at 15:12, Ingo Molnar wrote:
> * Lee Revell <rlrevell@joe-job.com> wrote:
>
> > Ok, first new one in a while. This was with -R0, but I haven't seen
> > anyone else report it. Let me know if you need the complete trace.
> >
> > preemption latency trace v1.0.2
> > -------------------------------
> > latency: 511 us, entries: 951 (951)
> > -----------------
> > | task: dbench/4810, uid:1000 nice:0 policy:0 rt_prio:0
> > -----------------
> > => started at: kill_pg_info+0x10/0x50
> > => ended at: kill_pg_info+0x2e/0x50
> > =======>
> > 00000001 0.000ms (+0.000ms): kill_pg_info (sys_kill)
> > 00000001 0.000ms (+0.000ms): __kill_pg_info (kill_pg_info)
> > 00000001 0.000ms (+0.000ms): find_pid (__kill_pg_info)
>
> this is quite hard to fix - lots of processes were SIGKILL-ed (or
> SIGTERM-ed) and the signal semantics require us to deliver signals
> atomically. The only fix would be to turn the signal locks into
> semaphores but that's quite hard. (it's also a bit problematic for
> interrupt-delivered signals.)
>
> Ingo
>

Here is a histogram I generated using realfeel2. This should provide
better data than my jackd histograms because the latter are dependent on
the ALSA driver, jackd's design, etc.

I had to modify the amlat utilities to use usecs instead of msecs, this
is a very good sign. ;-)

http://krustophenia.net/testresults.php?dataset=2.6.9-rc1-R0#/var/www/2.6.9-rc1-R0/foo.hist

I find the two smaller spikes to either side of the central spike really
odd. These showed up in my jackd tests too, I had attributed them to
some measurement artifact, but they seem real. Maybe a rounding bug, or
some kind of weird cache effect?

Lee


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