From: Andreas Dilger <adilger@clusterfs.com>
To: reiser <reiser@namesys.com>
Cc: Chris Mason <mason@suse.com>, JP Howard <jh_lists@fastmail.fm>,
Edward Shishkin <edward@namesys.com>,
ReiserFS List <reiserfs-list@namesys.com>,
Oleg Drokin <green@namesys.com>
Subject: Re: External journals and NVRAM devices
Date: Wed, 6 Nov 2002 13:18:32 -0700 [thread overview]
Message-ID: <20021106201832.GR588@clusterfs.com> (raw)
In-Reply-To: <3DC836D2.5060100@namesys.com>
On Nov 05, 2002 13:23 -0800, reiser wrote:
> Chris Mason wrote:
> >With ext3, a 128M or bigger log can really improve performance because
> >so much of the writeback is done through bdflush/kupdate.
>
> Please explain the because clause of the sentence above in more detail.
Nobody has answered this yet AFAIK, so I will.
The reason that having a large log can help performance is because
having bdflush drive the dirty buffer writeout allows for more changes
of write merging by the elevator and such, and also avoids stalls in
user-space code as it waits for a full journal to commit transactions.
There is a fine line here (for ext3 at least), because if you have a
large journal but it fills up before the transactions have been flushed
to the filesystem, then user apps stall while the journal is flushed
(can be several seconds).
Cheers, Andreas
--
Andreas Dilger
http://www-mddsp.enel.ucalgary.ca/People/adilger/
http://sourceforge.net/projects/ext2resize/
next prev parent reply other threads:[~2002-11-06 20:18 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-11-01 21:37 External journals and NVRAM devices JP Howard
2002-11-04 13:16 ` Chris Mason
2002-11-05 21:23 ` reiser
2002-11-06 20:18 ` Andreas Dilger [this message]
2002-11-06 20:42 ` Chris Mason
-- strict thread matches above, loose matches on Subject: below --
2002-11-05 22:12 JP Howard
2002-11-01 20:38 JP Howard
2002-11-01 20:57 ` Valdis.Kletnieks
2002-11-01 21:57 ` Edward Shishkin
2002-11-01 21:58 ` Edward Shishkin
2002-11-01 7:29 JP Howard
2002-11-01 7:49 ` Serge Kolodeznyh
2002-11-01 15:33 ` Len Sorensen
2002-11-01 15:10 ` Edward Shishkin
2002-11-01 5:38 Jeremy Howard
2002-11-01 6:29 ` Andreas Dilger
2002-11-01 14:30 ` Edward Shishkin
2002-11-01 20:40 ` Hans Reiser
2002-11-01 21:45 ` Edward Shishkin
2002-11-01 20:41 ` Hans Reiser
2002-11-02 3:04 ` Andrew Clausen
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