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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: Memory management woes - order 1 allocation failures
Cc: kosaki.motohiro@jp.fujitsu.com, Mel Gorman <mel@csn.ul.ie>,
       Pekka Enberg <penberg@cs.helsinki.fi>,
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Date: Wed,  3 Mar 2010 08:31:01 +0900 (JST)
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> > 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! :)