Message-ID: <43BBAF37.3060108@cosmosbay.com>
Date: Wed, 04 Jan 2006 12:19:19 +0100
From: Eric Dumazet <dada1@cosmosbay.com>
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To: Andi Kleen <ak@suse.de>
CC: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Shrinks sizeof(files_struct) and better layout
References: <20051108185349.6e86cec3.akpm@osdl.org> <p733bk4z2z0.fsf@verdi.suse.de> <43BBADD5.3070706@cosmosbay.com> <200601041215.36627.ak@suse.de>
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Andi Kleen a ?crit :
> On Wednesday 04 January 2006 12:13, Eric Dumazet wrote:
>> Andi Kleen a ?crit :
>>> Eric Dumazet <dada1@cosmosbay.com> writes:
>>>> 1) Reduces the size of (struct fdtable) to exactly 64 bytes on 32bits
>>>> platforms, lowering kmalloc() allocated space by 50%.
>>> It should be probably a kmem_cache_alloc() instead of a kmalloc
>>> in the first place anyways. This would reduce fragmentation.
>> Well in theory yes, if you really expect thousand of tasks running...
>> But for most machines, number of concurrent tasks is < 200, and using a 
>> special cache for this is not a win.
> 
> It is because it avoids fragmentation because objects with similar livetimes
> are clustered together. In general caches are a win
> if the data is nearly a page or more.

I dont undertand your last sentence. Do you mean 'if the object size is near 
PAGE_SIZE' ?

Eric
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