From: Dave Chinner <david@fromorbit.com>
To: Alex Elder <aelder@sgi.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 4/8] xfs: limit extent length for allocation to AG size
Date: Thu, 27 Jan 2011 11:38:52 +1100 [thread overview]
Message-ID: <20110127003851.GC21311@dastard> (raw)
In-Reply-To: <1296076968.1980.941.camel@doink>
On Wed, Jan 26, 2011 at 03:22:48PM -0600, Alex Elder wrote:
> On Tue, 2011-01-25 at 19:50 +1100, Dave Chinner wrote:
> > From: Dave Chinner <dchinner@redhat.com>
> >
> > Delayed allocation extents can be larger than AGs, so when trying to
> > convert a large range we may scan every AG inside
> > xfs_bmap_alloc_nullfb() trying to find an AG with a size larger than
> > an AG. We should stop when we find the first AG with a maximum
> > possible allocation size. This causes excessive CPU usage when there
> > are lots of AGs.
> >
> > The same problem occurs when doing preallocation of a range larger
> > than an AG.
> >
> > Fix the problem by limiting real allocation lengths to the maximum
> > that an AG can support. This means if we have empty AGs, we'll stop
> > the search at the first of them. If there are no empty AGs, we'll
> > still scan them all, but that is a different problem....
>
> Maybe I'm wrong but I think you need to change a "+"
> to a "-" (shown below).
Good catch. That's what I get for cleaning up code ;)
>
> And I have a few really minor suggestions:
> - You should update a comment (which I point
> out below) to match your change.
Will fix.
> - Maybe make use of a local variable, at least
> in xfs_bmap_btalloc_nullfb(), such as:
> xfs_extlen_t requested = args->maxlen;
All the allocation code is coded that way to avoid putting local
variables on the stack. The allocation-in-writeback path is the
critical stack usage path in XFS, so I'd prefer to keep using
args->maxlen here....
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2011-01-27 0:36 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-25 8:50 [PATCH 0/8] xfs: 2.6.38-rc candidate fixes V2 Dave Chinner
2011-01-25 8:50 ` [PATCH 1/8] xfs: fix log ticket leak on forced shutdown Dave Chinner
2011-01-26 21:22 ` Alex Elder
2011-01-25 8:50 ` [PATCH 2/8] xfs: fix efi item " Dave Chinner
2011-01-25 23:53 ` Christoph Hellwig
2011-01-27 0:35 ` Dave Chinner
2011-01-26 21:22 ` Alex Elder
2011-01-25 8:50 ` [PATCH 3/8] xfs: speculative delayed allocation uses rounddown_power_of_2 badly Dave Chinner
2011-01-26 21:22 ` Alex Elder
2011-01-25 8:50 ` [PATCH 4/8] xfs: limit extent length for allocation to AG size Dave Chinner
2011-01-26 21:22 ` Alex Elder
2011-01-27 0:38 ` Dave Chinner [this message]
2011-01-25 8:50 ` [PATCH 5/8] xfs: prevent extsize alignment from exceeding maximum extent size Dave Chinner
2011-01-25 9:49 ` Christoph Hellwig
2011-01-26 21:22 ` Alex Elder
2011-01-27 0:50 ` Dave Chinner
2011-01-25 8:50 ` [PATCH 6/8] xfs: limit extsize to size of AGs and/or MAXEXTLEN Dave Chinner
2011-01-26 21:23 ` Alex Elder
2011-01-25 8:50 ` [PATCH 7/8] xfs: handle CIl transaction commit failures correctly Dave Chinner
2011-01-25 9:53 ` Christoph Hellwig
2011-01-26 21:23 ` Alex Elder
2011-01-25 8:50 ` [PATCH 8/8] xfs: fix dquot shaker deadlock Dave Chinner
2011-01-25 9:52 ` Christoph Hellwig
2011-01-27 1:54 ` Dave Chinner
2011-01-27 2:24 ` Dave Chinner
2011-01-26 21:23 ` Alex Elder
2011-01-25 9:20 ` [PATCH 0/8] xfs: 2.6.38-rc candidate fixes V2 Christoph Hellwig
2011-01-26 21:23 ` Alex Elder
-- strict thread matches above, loose matches on Subject: below --
2011-01-27 3:53 [PATCH 0/8] xfs: candidate 2.6.38-rc fixes V3 Dave Chinner
2011-01-27 3:53 ` [PATCH 4/8] xfs: limit extent length for allocation to AG size Dave Chinner
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