linux-kernel - Re: [PATCH] lazy freeing of memory through MADV

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Date:	Sat, 21 Apr 2007 02:48:25 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Rik van Riel <riel@...hat.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>, shak <dshaks@...hat.com>
Subject: Re: [PATCH] lazy freeing of memory through MADV_FREE

Rik van Riel a écrit :
> Andrew Morton wrote:
>> On Fri, 20 Apr 2007 17:38:06 -0400
>> Rik van Riel <riel@...hat.com> wrote:
>>
>>> Andrew Morton wrote:
>>>
>>>> I've also merged Nick's "mm: madvise avoid exclusive mmap_sem".
>>>>
>>>> - Nick's patch also will help this problem.  It could be that your 
>>>> patch
>>>>   no longer offers a 2x speedup when combined with Nick's patch.
>>>>
>>>>   It could well be that the combination of the two is even better, 
>>>> but it
>>>>   would be nice to firm that up a bit.  
>>> I'll test that.
>>
>> Thanks.
> 
> Well, good news.
> 
> It turns out that Nick's patch does not improve peak
> performance much, but it does prevent the decline when
> running with 16 threads on my quad core CPU!
> 
> We _definately_ want both patches, there's a huge benefit
> in having them both.
> 
> Here are the transactions/seconds for each combination:
> 
>    vanilla   new glibc  madv_free kernel   madv_free + mmap_sem
> threads
> 
> 1     610         609             596                545

545 tps versus 610 tps for one thread ? It seems quite bad, no ?

Could you please find an explanation for this ?

> 2    1032        1136            1196               1200
> 4    1070        1128            2014               2024
> 8    1000        1088            1665               2087
> 16    779        1073            1310               1999
> 
> 

Thank you
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