From: Dave Chinner <david@fromorbit.com>
To: Mark Lord <kernel@teksavvy.com>
Cc: Christoph Hellwig <hch@infradead.org>,
xfs@oss.sgi.com, Linux Kernel <linux-kernel@vger.kernel.org>,
Alex Elder <aelder@sgi.com>
Subject: Re: xfs: very slow after mount, very slow at umount
Date: Fri, 28 Jan 2011 10:34:09 +1100 [thread overview]
Message-ID: <20110127233409.GL21311@dastard> (raw)
In-Reply-To: <4D40EC2D.5020507@teksavvy.com>
On Wed, Jan 26, 2011 at 10:53:17PM -0500, Mark Lord wrote:
> On 11-01-26 10:43 PM, Dave Chinner wrote:
> > On Wed, Jan 26, 2011 at 08:43:43PM -0500, Mark Lord wrote:
> >> On 11-01-26 08:22 PM, Mark Lord wrote:
> ..
> >> Thinking about it some more: the first problem very much appears as if
> >> it is due to a filesystem check happening on the already-mounted filesystem,
> >> if that makes any kind of sense (?).
> >
> > Not to me. You can check this simply by looking at the output of
> > top while the problem is occurring...
>
> Top doesn't show anything interesting, since disk I/O uses practically zero CPU.
My point is that xfs_check doesn't use zero cpu or memory - it uses
quite a lot of both, so if it is not present in top output while the
disk is being thrashed, it ain't running...
>
> >> running xfs_check on the umounted drive takes about the same 30-60 seconds,
> >> with the disk activity light fully "on".
> >
> > Well, yeah - XFS check reads all the metadata in the filesystem, so
> > of course it's going to thrash your disk when it is run. The fact it
> > takes the same length of time as whatever problem you are having is
> > likely to be coincidental.
>
> I find it interesting that the mount takes zero-time,
> as if it never actually reads much from the filesystem.
> Something has to eventually read the metadata etc.
Sure, for a clean log it has basically nothing to do - a few disk
reads to read the superblock, find the head/tail of the log, and
little else needs doing. Only when log recovery needs to be done
does mount do any significant IO.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Mark Lord <kernel@teksavvy.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Alex Elder <aelder@sgi.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
xfs@oss.sgi.com
Subject: Re: xfs: very slow after mount, very slow at umount
Date: Fri, 28 Jan 2011 10:34:09 +1100 [thread overview]
Message-ID: <20110127233409.GL21311@dastard> (raw)
In-Reply-To: <4D40EC2D.5020507@teksavvy.com>
On Wed, Jan 26, 2011 at 10:53:17PM -0500, Mark Lord wrote:
> On 11-01-26 10:43 PM, Dave Chinner wrote:
> > On Wed, Jan 26, 2011 at 08:43:43PM -0500, Mark Lord wrote:
> >> On 11-01-26 08:22 PM, Mark Lord wrote:
> ..
> >> Thinking about it some more: the first problem very much appears as if
> >> it is due to a filesystem check happening on the already-mounted filesystem,
> >> if that makes any kind of sense (?).
> >
> > Not to me. You can check this simply by looking at the output of
> > top while the problem is occurring...
>
> Top doesn't show anything interesting, since disk I/O uses practically zero CPU.
My point is that xfs_check doesn't use zero cpu or memory - it uses
quite a lot of both, so if it is not present in top output while the
disk is being thrashed, it ain't running...
>
> >> running xfs_check on the umounted drive takes about the same 30-60 seconds,
> >> with the disk activity light fully "on".
> >
> > Well, yeah - XFS check reads all the metadata in the filesystem, so
> > of course it's going to thrash your disk when it is run. The fact it
> > takes the same length of time as whatever problem you are having is
> > likely to be coincidental.
>
> I find it interesting that the mount takes zero-time,
> as if it never actually reads much from the filesystem.
> Something has to eventually read the metadata etc.
Sure, for a clean log it has basically nothing to do - a few disk
reads to read the superblock, find the head/tail of the log, and
little else needs doing. Only when log recovery needs to be done
does mount do any significant IO.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2011-01-27 23:31 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-27 1:22 xfs: very slow after mount, very slow at umount Mark Lord
2011-01-27 1:43 ` Mark Lord
2011-01-27 3:43 ` Dave Chinner
2011-01-27 3:43 ` Dave Chinner
2011-01-27 3:53 ` Mark Lord
2011-01-27 3:53 ` Mark Lord
2011-01-27 4:54 ` Mark Lord
2011-01-27 4:54 ` Mark Lord
2011-01-27 23:34 ` Dave Chinner [this message]
2011-01-27 23:34 ` Dave Chinner
2011-01-27 3:30 ` Dave Chinner
2011-01-27 3:30 ` Dave Chinner
2011-01-27 3:49 ` Mark Lord
2011-01-27 3:49 ` Mark Lord
2011-01-27 5:17 ` Stan Hoeppner
2011-01-27 15:12 ` Mark Lord
2011-01-27 15:12 ` Mark Lord
2011-01-27 15:40 ` Justin Piszcz
2011-01-27 15:40 ` Justin Piszcz
2011-01-27 16:03 ` Mark Lord
2011-01-27 16:03 ` Mark Lord
2011-01-27 19:40 ` Stan Hoeppner
2011-01-27 19:40 ` Stan Hoeppner
2011-01-27 20:11 ` david
2011-01-27 20:11 ` david
2011-01-27 23:53 ` Stan Hoeppner
2011-01-27 23:53 ` Stan Hoeppner
2011-01-28 2:09 ` david
2011-01-28 2:09 ` david
2011-01-28 13:56 ` Dave Chinner
2011-01-28 13:56 ` Dave Chinner
2011-01-28 19:26 ` david
2011-01-28 19:26 ` david
2011-01-29 5:40 ` Dave Chinner
2011-01-29 5:40 ` Dave Chinner
2011-01-29 6:08 ` david
2011-01-29 6:08 ` david
2011-01-29 7:35 ` Dave Chinner
2011-01-29 7:35 ` Dave Chinner
2011-01-31 19:17 ` Christoph Hellwig
2011-01-31 19:17 ` Christoph Hellwig
2011-01-27 21:56 ` Mark Lord
2011-01-27 21:56 ` Mark Lord
2011-01-28 0:17 ` Dave Chinner
2011-01-28 0:17 ` Dave Chinner
2011-01-28 1:22 ` Mark Lord
2011-01-28 1:22 ` Mark Lord
2011-01-28 1:36 ` Mark Lord
2011-01-28 1:36 ` Mark Lord
2011-01-28 4:14 ` David Rees
2011-01-28 4:14 ` David Rees
2011-01-28 14:22 ` Mark Lord
2011-01-28 14:22 ` Mark Lord
2011-01-28 7:31 ` Dave Chinner
2011-01-28 7:31 ` Dave Chinner
2011-01-28 14:33 ` Mark Lord
2011-01-28 14:33 ` Mark Lord
2011-01-28 23:58 ` Dave Chinner
2011-01-28 23:58 ` Dave Chinner
2011-01-28 19:18 ` Martin Steigerwald
2011-01-28 19:18 ` Martin Steigerwald
2011-01-27 20:24 ` John Stoffel
2011-01-27 20:24 ` John Stoffel
2011-01-27 23:41 ` Dave Chinner
2011-01-27 23:41 ` Dave Chinner
2011-01-28 0:59 ` Mark Lord
2011-01-28 0:59 ` Mark Lord
2011-01-27 23:39 ` Dave Chinner
2011-01-27 23:39 ` Dave Chinner
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