linux-kernel - Re: [PATCH -mm 00/24] VM pageout scalability improvements (V12)

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Date:	Thu, 12 Jun 2008 09:31:21 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org,
	Lee Schermerhorn <lee.schermerhorn@...com>,
	Kosaki Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: [PATCH -mm 00/24] VM pageout scalability improvements (V12)

On Wed, 11 Jun 2008 22:34:30 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On a 900MB 2-way, allocate and memset 1000MB.

> Seems to have saved a little CPU but the IO patterns got worse.

In previous tests on my 16GB system, a 16GB fillmem (goes into swap)
saves enough CPU time to make up for potentially worse detection of
the working set (well, not like this program really has a working set).

I'll try this out myself on a smaller system and see if there's
something I can do to make it better.
 
> qsbench, 4 processes, memory size tuned to threshold-of-swapping*1.1:
> 
> Mainline:
> 
> vmm:/home/akpm/qsbench> time ./qsbench -p 4 -m 230
> ./qsbench -p 4 -m 230  175.45s user 45.67s system 60% cpu 6:08.40 total
> 
> 2.6.26-rc5-mm3:
> 
> vmm:/home/akpm/qsbench> time ./qsbench -p 4 -m 230
> ./qsbench -p 4 -m 230  178.21s user 28.49s system 99% cpu 3:27.14 total
> 
> So woot!  Professional qsbench users will be pleased ;) It could have
> been a fluke though - iirc qsbench is pretty unstable, especially on
> the threshold.

Ignoring references that happen on the active list, only acting
on re-references that happen on the inactive list, gives anonymous
memory something that closer resembles the use-once policy.

Better for some workloads, but potentially worse for others.

Definately worth tweaking the system though, to get performance
as close to where we want it as possible :)

> Main thing is: it seems stable.  Old LTP ran for an hour or so before I
> hit the msgctl08 crash (which is a regression in current mainline).

Our main focus has been on stability for the past few months,
trying to get the whole series integrated.

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