From: Christoph Hellwig <hch@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>, bpm@sgi.com, xfs@oss.sgi.com
Subject: Re: Issues with delalloc->real extent allocation
Date: Thu, 20 Jan 2011 06:16:12 -0500 [thread overview]
Message-ID: <20110120111612.GA14571@infradead.org> (raw)
In-Reply-To: <20110120013346.GO16267@dastard>
On Thu, Jan 20, 2011 at 12:33:46PM +1100, Dave Chinner wrote:
> It's case b) that I'm mainly worried about, esp. w.r.t the 64k page
> size on ia64/ppc. If we only track a single dirty bit in the page,
> then every sub-page, non-appending write to an uncached region of a
> file becomes a RMW cycle to initialise the areas around the write
> correctly. The question is whether we care about this enough given
> that we return at least PAGE_SIZE in stat() to tell applications the
> optimal IO size to avoid RMW cycles.
Note that this generally is only true for the first write into the
region - after that we'll have the rest read into the cache. But
we also have the same issue for appending writes if they aren't
page aligned.
> And if we only do IO on whole pages (i.e regardless of block size)
> .writepage suddenly becomes a lot simpler, as well as being trivial
> to implement our own .readpage/.readpages....
I don't think it simplifies writepage a lot. All the buffer head
handling goes away, but we'll still need to do xfs_bmapi calls at
block size granularity. Why would you want to replaced the
readpage/readpages code? The generic mpage helpers for it do just fine.
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next prev parent reply other threads:[~2011-01-20 11:13 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-14 0:29 Issues with delalloc->real extent allocation Dave Chinner
2011-01-14 16:40 ` Geoffrey Wehrman
2011-01-14 22:59 ` Dave Chinner
2011-01-15 4:16 ` Geoffrey Wehrman
2011-01-17 5:18 ` Dave Chinner
2011-01-17 14:37 ` Geoffrey Wehrman
2011-01-18 0:24 ` Dave Chinner
2011-01-18 14:30 ` Geoffrey Wehrman
2011-01-18 20:40 ` Christoph Hellwig
2011-01-18 22:03 ` Dave Chinner
2011-01-14 21:43 ` bpm
2011-01-14 23:32 ` bpm
2011-01-14 23:50 ` bpm
2011-01-14 23:55 ` Dave Chinner
2011-01-17 20:12 ` bpm
2011-01-18 1:44 ` Dave Chinner
2011-01-18 20:47 ` Christoph Hellwig
2011-01-18 23:18 ` Dave Chinner
2011-01-19 12:03 ` Christoph Hellwig
2011-01-19 13:31 ` Dave Chinner
2011-01-19 13:55 ` Christoph Hellwig
2011-01-20 1:33 ` Dave Chinner
2011-01-20 11:16 ` Christoph Hellwig [this message]
2011-01-21 1:59 ` Dave Chinner
2011-01-20 14:45 ` Geoffrey Wehrman
2011-01-21 2:51 ` Dave Chinner
2011-01-21 14:41 ` Geoffrey Wehrman
2011-01-23 23:26 ` Dave Chinner
2011-01-17 0:28 ` Lachlan McIlroy
2011-01-17 4:37 ` Dave Chinner
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