linux-kernel - Re: [ANNOUNCE] 2.6.31-rc6-rt2

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Date:	Tue, 18 Aug 2009 17:17:51 -0700
From:	john stultz <johnstul@...ibm.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	rt-users <linux-rt-users@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Carsten Emde <ce@...g.ch>,
	Clark Williams <williams@...hat.com>,
	Frank Rowand <frank.rowand@...sony.com>,
	Robin Gareus <robin@...eus.org>,
	Gregory Haskins <ghaskins@...ell.com>,
	Philippe Reynes <philippe.reynes@...smpp.fr>,
	Fernando Lopez-Lezcano <nando@...ma.stanford.edu>,
	Will Schmidt <will_schmidt@...t.ibm.com>,
	Darren Hart <dvhltc@...ibm.com>, Jan Blunck <jblunck@...e.de>,
	Sven-Thorsten Dietrich <sdietrich@...ell.com>,
	Jon Masters <jcm@...hat.com>
Subject: Re: [ANNOUNCE] 2.6.31-rc6-rt2

On Tue, Aug 18, 2009 at 3:50 PM, john stultz<johnstul@...ibm.com> wrote:
> On Tue, Aug 18, 2009 at 3:31 PM, john stultz<johnstul@...ibm.com> wrote:
>> I'm seeing some bad scheduler behavior with this patch. I've seen
>> occasional bad behavior with 2.6.29-rt as well, but with .31-rt its
>> much worse.
>>
>> I'm running a SCHED_OTHER cpubound benchmark  (censored to
>> xxxxxxxxxxxxx in the logs) that runs for a number of minutes. With
>> 2.6.31-rc6 I'm seeing really poor numbers and if I cat
>> /proc/sched_debug I see all of the cpu bound tasks are  running on the
>> same cpu, while the other procs are basically idle. See the log below:
>
> Thomas didn't like that I censored the benchmark, so until I know
> better about what I can say there, I've reproduced a similar effect
> with a make -j8 bzImage. See below:

Same thing happens w/ 2.6.31-rc6-rt4. config attached.

Simple busy loops like:
while true; do ls > /dev/null; done &
while true; do ls > /dev/null; done &
while true; do ls > /dev/null; done &
while true; do ls > /dev/null; done &

Also show the same behavior.

thanks
-john

View attachment "config.rt" of type "text/vnd.rn-realtext" (57472 bytes)