Re: Kernel 2.6.8.1: swap storm of death - CFQ scheduler=culprit

Marcelo Tosatti
2004-08-24T10:51:26Z

On Tue, Aug 24, 2004 at 12:03:43PM +0200, Jens Axboe wrote:
> On Mon, Aug 23 2004, Karl Vogel wrote:
> > > > Jens, is this huge amount of bio/biovec's allocations
> > > expected with CFQ? Its really really bad.
> > >
> > > Nope, it's not by design :-)
> > >
> > > A test case would be nice, then I'll fix it as soon as possible. But
> > > please retest with 2.6.8.1 marcelo, 2.6.8-rc4 is missing an important
> > > fix to ll_rw_blk that can easily cause this. The first report is for
> > > 2.6.8.1, so I'm more puzzled on that.
> >
> > I tried with 2.6.8.1 and 2.6.8.1-mm4, both had the problem. If there
> > is anything extra I need to try/record, just shoot!
> >
> > Original post with testcase + stats:
> > http://article.gmane.org/gmane.linux.kernel/228156
>
> 2.6.8.1-mm4 clean does not reproduce the problem. Marcelo, your
> 2.6.8-rc4 report is not valid due to the fixed problem related to that
> in CFQ already. I'd still like for you to retest with 2.6.8.1.
>
> So I'm trying 2.6.8.1 with voluntary preempt applied now, the bug could
> be related to that.

Jens,

You are right, I've been unable to reproduce the problem I was seeing
(huge amount of bio/biovec's allocation causing major swapouts) with
2.6.8.1.

With this kernel, The 512MB system swaps around 50MB and recovers perfectly,
I can't see any odd behaviour with CFQ.