linux-kernel - Re: [BUG] scheduler: first timeslice of the exiting thread

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Message-ID: <87slb8y9xe.wl%takeuchi_satoru@jp.fujitsu.com>
Date:	Tue, 10 Apr 2007 16:18:21 +0900
From:	Satoru Takeuchi <takeuchi_satoru@...fujitsu.com>
To:	Mike Galbraith <efault@....de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Satoru Takeuchi <takeuchi_satoru@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Con Kolivas <kernel@...ivas.org>
Subject: Re: [BUG] scheduler: first timeslice of the exiting thread

> > This comes at an awkward time, because we might well merge the
> > staircase/deadline work into 2.6.22, and I think it rewrites the part of
> > the scheduler which is causing the problems you're observing.
> > 
> > Has anyone verified that SD fixes this problem and the one at
> > http://lkml.org/lkml/2007/4/7/21 ?
> 
> Not verified either way in testing, but I believe this should be a
> problem for SD as well because timeslice fork/exit handling is identical
> with mainline.  Individual slices are much smaller than mainline, so
> priority should drop rapidly, consuming bandwidth allotted for the
> current rotation, sending the creator off to the expired array
> prematurely.
> 
> 	-Mike
> 

Yes, this probelm also occurs on the SD. Here is the 2.6.21-rc6-mm1's
trace.

Process model:

fork: pid = 12431, tgid = 12431, ppid = 2737, time_slice = 8000000
exit: pid = 12431, tgid = 12431, ppid = 12430, time_slice = 3842675
fork: pid = 12432, tgid = 12432, ppid = 2737, time_slice = 6175786
exit: pid = 12432, tgid = 12432, ppid = 12430, time_slice = 2948968
fork: pid = 12433, tgid = 12433, ppid = 2737, time_slice = 5862607
exit: pid = 12433, tgid = 12433, ppid = 12430, time_slice = 2793696
fork: pid = 12434, tgid = 12434, ppid = 2737, time_slice = 5515983
exit: pid = 12434, tgid = 12434, ppid = 12430, time_slice = 2583218
fork: pid = 12435, tgid = 12435, ppid = 2737, time_slice = 5174253
exit: pid = 12435, tgid = 12435, ppid = 12430, time_slice = 2421119
fork: pid = 12436, tgid = 12436, ppid = 2737, time_slice = 4433521
exit: pid = 12436, tgid = 12436, ppid = 12430, time_slice = 2068271
fork: pid = 12437, tgid = 12437, ppid = 2737, time_slice = 4115828
exit: pid = 12437, tgid = 12437, ppid = 12430, time_slice = 1906364
fork: pid = 12438, tgid = 12438, ppid = 2737, time_slice = 3817721
exit: pid = 12438, tgid = 12438, ppid = 12430, time_slice = 1763586
fork: pid = 12439, tgid = 12439, ppid = 2737, time_slice = 3523880
exit: pid = 12439, tgid = 12439, ppid = 12430, time_slice = 1621289
fork: pid = 12440, tgid = 12440, ppid = 2737, time_slice = 2856168
exit: pid = 12440, tgid = 12440, ppid = 12430, time_slice = 1269502
exit: pid = 12430, tgid = 12430, ppid = 2737, time_slice = 2434379

Thread model:

fork: pid = 12554, tgid = 12553, ppid = 2737, time_slice = 2841904
exit: pid = 12554, tgid = 12553, ppid = 2737, time_slice = 1420952
fork: pid = 12555, tgid = 12553, ppid = 2737, time_slice = 29977
exit: pid = 12555, tgid = 12553, ppid = 2737, time_slice = 14988
fork: pid = 12556, tgid = 12553, ppid = 2737, time_slice = 8000000
exit: pid = 12556, tgid = 12553, ppid = 2737, time_slice = 4000000
fork: pid = 12557, tgid = 12553, ppid = 2737, time_slice = 3976416
exit: pid = 12557, tgid = 12553, ppid = 2737, time_slice = 1988208
fork: pid = 12558, tgid = 12553, ppid = 2737, time_slice = 1965192
exit: pid = 12558, tgid = 12553, ppid = 2737, time_slice = 982596
fork: pid = 12559, tgid = 12553, ppid = 2737, time_slice = 955481
exit: pid = 12559, tgid = 12553, ppid = 2737, time_slice = 477740
fork: pid = 12560, tgid = 12553, ppid = 2737, time_slice = 453317
exit: pid = 12560, tgid = 12553, ppid = 2737, time_slice = 226658
fork: pid = 12561, tgid = 12553, ppid = 2737, time_slice = 203189
exit: pid = 12561, tgid = 12553, ppid = 2737, time_slice = 101594
fork: pid = 12562, tgid = 12553, ppid = 2737, time_slice = 76756
exit: pid = 12562, tgid = 12553, ppid = 2737, time_slice = 38378
fork: pid = 12563, tgid = 12553, ppid = 2737, time_slice = 15096
exit: pid = 12563, tgid = 12553, ppid = 2737, time_slice = 7548
exit: pid = 12553, tgid = 12553, ppid = 2737, time_slice = 7851311

NOTE: Nanosecond is the unit of time_slice on SD, so the time_slice
      value is very differ from the current scheduler's one.

Satoru
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