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From: Jens Axboe <jens.axboe@oracle.com>
To: Theodore Tso <tytso@mit.edu>
Cc: Christoph Hellwig <hch@infradead.org>,
	Dave Chinner <david@fromorbit.com>,
	Chris Mason <chris.mason@oracle.com>,
	linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	xfs@oss.sgi.com
Subject: Re: ext4 writepages is making tiny bios?
Date: Fri, 4 Sep 2009 09:20:13 +0200	[thread overview]
Message-ID: <20090904072013.GR18599@kernel.dk> (raw)
In-Reply-To: <20090904001545.GA30759@mit.edu>

On Thu, Sep 03 2009, Theodore Tso wrote:
> On Thu, Sep 03, 2009 at 12:42:09PM -0400, Christoph Hellwig wrote:
> > > Careful:
> > > 
> > > -	tloff = min(tlast, startpage->index + 64);
> > > +	tloff = min(tlast, startpage->index + 8192);
> > > 
> > > That will cause 64k page machines to try to write back 512MB at a
> > > time. This will re-introduce similar to the behaviour in sles9 where
> > > writeback would only terminate at the end of an extent (because the
> > > mapping end wasn't capped like above).
> > 
> > Pretty good point, any applies to all the different things we discussed
> > recently.  Ted, should be maybe introduce a max_writeback_mb instead of
> > the max_writeback_pages in the VM, too?
> 
> Good point.
> 
> Jens, maybe we should replace my patch with this one, which makes the
> tunable in terms of megabytes instead of pages?

That is probably a better metric than 'pages', lets update it.

-- 
Jens Axboe


WARNING: multiple messages have this Message-ID (diff)
From: Jens Axboe <jens.axboe@oracle.com>
To: Theodore Tso <tytso@mit.edu>
Cc: xfs@oss.sgi.com, Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
	Chris Mason <chris.mason@oracle.com>
Subject: Re: ext4 writepages is making tiny bios?
Date: Fri, 4 Sep 2009 09:20:13 +0200	[thread overview]
Message-ID: <20090904072013.GR18599@kernel.dk> (raw)
In-Reply-To: <20090904001545.GA30759@mit.edu>

On Thu, Sep 03 2009, Theodore Tso wrote:
> On Thu, Sep 03, 2009 at 12:42:09PM -0400, Christoph Hellwig wrote:
> > > Careful:
> > > 
> > > -	tloff = min(tlast, startpage->index + 64);
> > > +	tloff = min(tlast, startpage->index + 8192);
> > > 
> > > That will cause 64k page machines to try to write back 512MB at a
> > > time. This will re-introduce similar to the behaviour in sles9 where
> > > writeback would only terminate at the end of an extent (because the
> > > mapping end wasn't capped like above).
> > 
> > Pretty good point, any applies to all the different things we discussed
> > recently.  Ted, should be maybe introduce a max_writeback_mb instead of
> > the max_writeback_pages in the VM, too?
> 
> Good point.
> 
> Jens, maybe we should replace my patch with this one, which makes the
> tunable in terms of megabytes instead of pages?

That is probably a better metric than 'pages', lets update it.

-- 
Jens Axboe

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  reply	other threads:[~2009-09-04  7:20 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-09-01 18:44 ext4 writepages is making tiny bios? Chris Mason
2009-09-01 20:57 ` Theodore Tso
2009-09-01 21:27   ` Christoph Hellwig
2009-09-02  0:17     ` Chris Mason
2009-09-03  5:52     ` Dave Chinner
2009-09-03 16:42       ` Christoph Hellwig
2009-09-03 16:42         ` Christoph Hellwig
2009-09-04  0:15         ` Theodore Tso
2009-09-04  0:15           ` Theodore Tso
2009-09-04  7:20           ` Jens Axboe [this message]
2009-09-04  7:20             ` Jens Axboe

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