linux-ext4 - Re: [PATCH 1/2] ext2: speed up file creates by optimizing rec

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Message-Id: <63DB7A38-7D0F-406E-8ACD-9CE5DB977DD9@dilger.ca>
Date:	Wed, 8 Dec 2010 12:01:51 -0700
From:	Andreas Dilger <adilger.kernel@...ger.ca>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Eric Sandeen <sandeen@...hat.com>,
	ext4 development <linux-ext4@...r.kernel.org>,
	Jan Kara <jack@...e.cz>
Subject: Re: [PATCH 1/2] ext2: speed up file creates by optimizing rec_len functions

On 2010-12-07, at 14:33, Andrew Morton wrote:
> On Tue, 07 Dec 2010 15:22:55 -0600
> Eric Sandeen <sandeen@...hat.com> wrote:
>> Retesting at a bunch of different number-of-files in bonnie
>> (with a small sample size so probably a little noise)
>> 
>> 	|files per sec|
>> files	stock	patched	delta
>> 10,000	12300	14700	+19%
>> 20,000	 6300	 7600	+20%
>> 30,000	 4200	 5000	+20%
>> 40,000	 3150	 3700	+17%
>> 50,000	 2500	 3000	+20%
>> 
>> (again all on a 512MB ramdisk)
>> 
>> *shrug* I'll believe my lyin' eyes, I guess. :)
> 
> I bet other tweaks in there would yield similar goodliness.

I think an important factor here is that this is being tested on a ramdisk, and is likely CPU bound, so any CPU reduction will directly be measured as a performance improvement.  Probably oprofile is in order to see where other major CPU users are.

In the past, ext3_mark_inode_dirty() was a major offender, and I recall that we discussed on the ext4 concall a mechanism to only copy the inode once per transaction so that overhead could be removed.

Cheers, Andreas





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