linux-kernel - Re: find_busiest_group using lots of CPU

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Message-ID: <20091006121425.GA24070@elte.hu>
Date:	Tue, 6 Oct 2009 14:14:26 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Jens Axboe <jens.axboe@...cle.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: find_busiest_group using lots of CPU


* Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:

> On Tue, 2009-10-06 at 13:20 +0200, Jens Axboe wrote:
> > > > io_schedule() straight into find_busiest_group() leads me to think this
> > > > could be SD_BALANCE_NEWIDLE, does something like:
> > > > 
> > > > for i in /proc/sys/kernel/sched_domain/cpu*/domain*/flags; 
> > > > do 
> > > >     val=`cat $i`; echo $((val & ~0x02)) > $i; 
> > > > done
> > > > 
> > > > [ assuming SCHED_DEBUG=y ]
> > > > 
> > > > Cure things?
> > > 
> > > I can try,
> > 
> > It does, it's gone from the profiles.
> 
> Hrmm,. ok. I'll go prod at the NEWIDLE bits to see if anything stands
> out.
> 
> If only perf-annotate could generate annotated C... maybe I'll look at 
> that.

hey it can do that - build a vmlinux with DEBUG_INFO=y and it should 
just work :-)

	Ingo
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