linux-kernel - Re: Memory management woes - order 1 allocation failures

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Message-Id: <20100303082239.D614.A69D9226@jp.fujitsu.com>
Date:	Wed,  3 Mar 2010 08:31:01 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	kosaki.motohiro@...fujitsu.com, Mel Gorman <mel@....ul.ie>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Frans Pop <elendil@...net.nl>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Mel Gorman <mel@...net.ie>
Subject: Re: Memory management woes - order 1 allocation failures

> > For reasons that are not particularly clear to me, tty_buffer_alloc() is
> > called far more frequently in 2.6.33 than in 2.6.24. I instrumented the
> > function to print out the size of the buffers allocated, booted under
> > qemu and would just "cat /bin/ls" to see what buffers were allocated.
> > 2.6.33 allocates loads, including high-order allocations. 2.6.24
> > appeared to allocate once and keep silent.
> 
> The pty layer is using them now and didn't before. That will massively
> distort your numhers.
> 
> > While there have been snags recently with respect to high-order
> > allocation failures in recent kernels, this might be one of the cases
> > where it's due to subsystems requesting high-order allocations more.
> 
> The pty code certainly triggered more such allocations. I've sent Greg
> patches to make the tty buffering layer allocate sensible sizes as it
> doesn't need multiple page allocations in the first place.

Wow, great! :)


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