From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Pekka J Enberg <penberg@cs.helsinki.fi>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-ext4@vger.kernel.org, cl@linux-foundation.org,
mpm@selenic.com, eduard.munteanu@linux360.ro
Subject: Re: [PATCH] ext2/ext3: allocate ->s_blockgroup_lock separately to avoid wasting space
Date: Sun, 16 Nov 2008 13:58:09 +0100 [thread overview]
Message-ID: <1226840289.8172.8.camel@lappy.programming.kicks-ass.net> (raw)
In-Reply-To: <Pine.LNX.4.64.0811141115100.29826@melkki.cs.Helsinki.FI>
On Fri, 2008-11-14 at 11:17 +0200, Pekka J Enberg wrote:
> From: Pekka Enberg <penberg@cs.helsinki.fi>
>
> As spotted by kmemtrace, struct ext2_sb_info is 17024 bytes and ext3_sb_info is
> 17152 bytes on 64-bit which makes them a very bad fit for SLAB allocators. In
> fact, both allocations are round up to the next available page size of
> order 3 which is 32 KB.
>
> The culprit if the wasted memory is the ->s_blockgroup_lock which can be as big
> as 16 KB when CONFIG_NR_CPUS is set to 32. As struct blockgroup_lock is a
> perfect fit for order 2 page in the worst case, allocate ->s_blockgroup_lock
> separately to avoid wasting space.
And here I was thinking that NR_CPUS=4096 is currently our worst
case ;-)
next prev parent reply other threads:[~2008-11-16 12:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-14 9:17 [PATCH] ext2/ext3: allocate ->s_blockgroup_lock separately to avoid wasting space Pekka J Enberg
2008-11-14 21:26 ` Andreas Dilger
2008-11-16 12:58 ` Peter Zijlstra [this message]
2008-11-17 21:27 ` Pekka Enberg
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