linux-ext4 - Re: [PATCH] ext4: Don't allow lg prealloc list to be grow large.

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Message-ID: <48861BFF.5050108@redhat.com>
Date:	Tue, 22 Jul 2008 12:42:23 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
CC:	cmm@...ibm.com, tytso@....edu, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4: Don't allow lg prealloc list to be grow large.

Aneesh Kumar K.V wrote:
> Currently locality group prealloc list is freed only when there is a block allocation
> failure. This can result in large number of per cpu locality group prealloc space
> and also make the ext4_mb_use_preallocated expensive. Convert the locality group
> prealloc list to a hash list. The hash index is the order of number of blocks
> in the prealloc space with a max order of 9. When adding prealloc space to the
> list we make sure total entries for each order does not exceed 8. If it is more
> than 8 we discard few entries and make sure the we have only <= 5 entries.
> 

This looks better on the particular benchmark:

http://people.redhat.com/esandeen/ext4/fs_mark.png

contains a run with this patch.

I must admit to not actually reading the patch yet, though :)  Just ran
it in the background while working on some other things today.

-Eric
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