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

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Message-ID: <4CFFF394.1020303@redhat.com>
Date:	Wed, 08 Dec 2010 15:07:32 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	Andreas Dilger <adilger.kernel@...ger.ca>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	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 12/08/2010 01:01 PM, Andreas Dilger wrote:
> 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.

Yep, I ran oprofile.

samples  %        app name                 symbol name
1140046  41.8702  ext2.ko                  ext2_find_entry
1052117  38.6408  ext2.ko                  ext2_add_link
98424     3.6148  vmlinux                  native_safe_halt
40461     1.4860  vmlinux                  wait_on_page_read
29084     1.0682  vmlinux                  find_get_page

pretty slammed on those 2 ext2 functions!  I think it's pretty
overwhelmed by the linear search.

-Eric

> 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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