linux-kernel - Re: [PATCH] MM: implement MADV_FREE lazy freeing of anonymous memory

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Date:	Sat, 05 May 2007 09:49:26 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Rik van Riel <riel@...hat.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ulrich Drepper <drepper@...hat.com>,
	Jakub Jelinek <jakub@...hat.com>
Subject: Re: [PATCH] MM: implement MADV_FREE lazy freeing of anonymous memory

Rik van Riel wrote:
> Nick Piggin wrote:
> 
>> Rik van Riel wrote:
>>
>>> With lazy freeing of anonymous pages through MADV_FREE, performance of
>>> the MySQL sysbench workload more than doubles on my quad-core system.
>>
>>
>> OK, I've run some tests on a 16 core Opteron system, both sysbench with
>> MySQL 5.33 (set up as described in the freebsd vs linux page), and with
>> ebizzy.
>>
>> What I found is that, on this system, MADV_FREE performance improvement
>> was in the noise when you look at it on top of the MADV_DONTNEED glibc
>> and down_read(mmap_sem) patch in sysbench.
> 
> 
> Interesting, very different results from my system.
> 
> First, did you run with the properly TLB batched version of
> the MADV_FREE patch?  And did you make sure that MADV_FREE
> takes the mmap_sem for reading?   Without that, I did see
> a similar thing to what you saw...

Yes and yes (I initially forgot to add MADV_FREE to the down_read
case and saw horrible performance!)


> Secondly, I'll have to try some test runs one of the larger
> systems in the lab.
> 
> Maybe the results from my quad core Intel system are not
> typical; maybe the results from your 16 core Opteron are
> not typical.  Either way, I want to find out :)

Yep. We might have something like that here, and I'll try with
some other architectures as well next week, if I can get glibc
built.

-- 
SUSE Labs, Novell Inc.
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