From: Dave Chinner <david@fromorbit.com>
To: Brian Candler <brian@soundmouse.com>
Cc: Christoph Hellwig <hch@infradead.org>, xfs@oss.sgi.com
Subject: Re: Performance problem - reads slower than writes
Date: Wed, 1 Feb 2012 14:59:15 +1100 [thread overview]
Message-ID: <20120201035915.GS9090@dastard> (raw)
In-Reply-To: <20120131215210.GB47420@soundmouse.com>
On Tue, Jan 31, 2012 at 09:52:10PM +0000, Brian Candler wrote:
> On Tue, Jan 31, 2012 at 09:52:05AM -0500, Christoph Hellwig wrote:
> > You don't just read a single file at a time but multiple ones, don't
> > you?
>
> It's sequential at the moment, although I'll do further tests with the -c
> (concurrency) option to bonnie++
>
> > Try playing with the following tweaks to get larger I/O to the disk:
> >
> > a) make sure you use the noop or deadline elevators
> > b) increase /sys/block/sdX/queue/max_sectors_kb from its low default
> > c) dramatically increase /sys/devices/virtual/bdi/<major>:<minor>/read_ahead_kb
>
> Thank you very much: I will do further tests with these.
>
> Is the read_ahead_kb knob aware of file boundaries? That is, is there any
> risk that if I set it too large it would read useless blocks past the end of
> the file?
Yes, readahead only occurs within the file, and won't readahead past
EOF.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2012-02-01 3:59 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-30 22:00 Performance problem - reads slower than writes Brian Candler
2012-01-31 2:05 ` Dave Chinner
2012-01-31 10:31 ` Brian Candler
2012-01-31 14:16 ` Brian Candler
2012-01-31 20:25 ` Dave Chinner
2012-02-01 7:29 ` Stan Hoeppner
2012-02-03 18:47 ` Brian Candler
2012-02-03 19:03 ` Christoph Hellwig
2012-02-03 21:01 ` Brian Candler
2012-02-03 21:17 ` Brian Candler
2012-02-05 22:50 ` Dave Chinner
2012-02-05 22:43 ` Dave Chinner
2012-01-31 14:52 ` Christoph Hellwig
2012-01-31 21:52 ` Brian Candler
2012-02-01 0:50 ` Raghavendra D Prabhu
2012-02-01 3:59 ` Dave Chinner [this message]
2012-02-03 11:54 ` Brian Candler
2012-02-03 19:42 ` Stan Hoeppner
2012-02-03 22:10 ` Brian Candler
2012-02-04 9:59 ` Stan Hoeppner
2012-02-04 11:24 ` Brian Candler
2012-02-04 12:49 ` Stan Hoeppner
2012-02-04 20:04 ` Brian Candler
2012-02-04 20:44 ` Joe Landman
2012-02-06 10:40 ` Brian Candler
2012-02-07 17:30 ` Brian Candler
2012-02-05 5:16 ` Stan Hoeppner
2012-02-05 9:05 ` Brian Candler
2012-01-31 20:06 ` Dave Chinner
2012-01-31 21:35 ` Brian Candler
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