linux-ext4 - Re: [PATCHSET v2] ext4: removal of alloc_sem locks from block allocation paths

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Date:	Tue, 10 May 2011 15:48:58 +0200 (CEST)
From:	Lukas Czerner <lczerner@...hat.com>
To:	amir73il@...rs.sourceforge.net
cc:	tytso@....edu, linux-ext4@...r.kernel.org
Subject: Re: [PATCHSET v2] ext4: removal of alloc_sem locks from block
 allocation paths

On Thu, 24 Mar 2011, amir73il@...rs.sourceforge.net wrote:

> The purpose of this patch set is the removal of grp->alloc_sem locks
> from block allocation paths.
> 
> The resulting code is cleaner and should perform better in concurrent
> allocating tasks workloads.
Hi Amir,

Do you have any performance numbers indicating performance improvement
in concurrent allocations ? The only point where I can see taking
write semaphore is in filesystem resize code. Or am I missing something ?

Thanks!
-Lukas

> 
> I ran several xfstests runs with these patches (4K and 1K block size).
> I tried several online resizes and verifyed that both in-core and on-disk
> group counters are correct.
> 
> v2->v1:
> - fix silly bug in patch 4/5 that triggers BUG_ON(incore == NULL)
> - replace get_undo_access() with get_write_access()
> - ran xfstests with block size 1K (where 2 groups share a buddy page)
> 
> [PATCH v2 1/5] ext4: move ext4_add_groupblocks() to mballoc.c
> [PATCH v2 2/5] ext4: implement ext4_add_groupblocks() by freeing blocks
> [PATCH v2 3/5] ext4: synchronize ext4_mb_init_group() with buddy page lock
> [PATCH v2 4/5] ext4: teach ext4_mb_init_cache() to skip uptodate buddy caches
> [PATCH v2 5/5] ext4: remove alloc_semp
> 
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