linux-kernel - Re: [PATCH] slab: fix slab flags for archs use alignment larger 64-bit

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Message-ID: <4995565D.5010105@st.com>
Date:	Fri, 13 Feb 2009 12:15:41 +0100
From:	Giuseppe CAVALLARO <peppe.cavallaro@...com>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Paul Mundt <lethal@...ux-sh.org>, linux-kernel@...r.kernel.org,
	linux-sh@...r.kernel.org, linux-mm@...r.kernel.org,
	Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: [PATCH] slab: fix slab flags for archs use alignment larger 
 64-bit

Pekka Enberg wrote:
> Hi Giuseppe,
>
> On Fri, Feb 13, 2009 at 12:46 PM, Giuseppe CAVALLARO
> <peppe.cavallaro@...com> wrote:
>   
>> 1) LOG with my patch:
>> root@...ux:~# cat /proc/meminfo | grep Slab
>> Slab:             2612 kB
>>
>> 2) LOG without my patch:
>> root@...ux:~# cat /proc/meminfo | grep Slab
>> Slab:             2504 kB
>>     
>
> That's not too bad. I assume it's L1_CACHE_BYTES set to 32 bytes? 
you are perfectly right.
> One big problem with your patch is that on some MIPS configurations
> ARCH_KMALLOC_MINALIGN is as big as 128.
Agree again and problem understood... thanks!
> So if you're going to do this, you can't use ARCH_KMALLOC_MINALIGN directly but add a some
> SLAB_MAX_DEBUG_ALIGN which can be overridden by architecture code.
>   
If you like, I can prepare a patch in any case.
Then we can decide if it actually adds complexity and discard it.
Otherwise we could maintain it.
> One obvious question, though, is whether all this is worth the added
> complexity. I mean, we've managed "just fine" without it for years.
> Paul, thoughts?
>
>                                         Pekka
>
>   

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