From: Christoph Hellwig <hch@infradead.org>
To: Brian Candler <B.Candler@pobox.com>
Cc: xfs@oss.sgi.com
Subject: Re: Performance problem - reads slower than writes
Date: Tue, 31 Jan 2012 09:52:05 -0500 [thread overview]
Message-ID: <20120131145205.GA6607@infradead.org> (raw)
In-Reply-To: <20120131103126.GA46170@nsrc.org>
On Tue, Jan 31, 2012 at 10:31:26AM +0000, Brian Candler wrote:
> - seek to inode (if the inode block isn't already in cache)
> - seek to extents table (if all extents don't fit in the inode)
> - seek(s) to the file contents, depending on how they're fragmented.
>
> I am currently seeing somewhere between 7 and 8 seeks per file read, and
> this just doesn't seem right to me.
You don't just read a single file at a time but multiple ones, don't
you?
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
> OK. I saw "df -i" reporting a stupid number of available inodes, over 500
> million, so I decided to reduce it to 100 million. But df -k didn't show
> any corresponding increase in disk space, so I'm guessing in xfs these are
> allocated on-demand, and the inode limit doesn't really matter?
Exactly, the number displayed is the upper bound.
_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs
next prev parent reply other threads:[~2012-01-31 14:52 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 [this message]
2012-01-31 21:52 ` Brian Candler
2012-02-01 0:50 ` Raghavendra D Prabhu
2012-02-01 3:59 ` Dave Chinner
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120131145205.GA6607@infradead.org \
--to=hch@infradead.org \
--cc=B.Candler@pobox.com \
--cc=xfs@oss.sgi.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.