Messages in this thread | | | Date | Tue, 15 Jun 2010 06:57:40 -0400 | From | Christoph Hellwig <> | Subject | Re: [PATCH 11/12] vmscan: Write out dirty pages in batch |
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On Mon, Jun 14, 2010 at 04:21:43PM -0700, Andrew Morton wrote: > Yup. > > But then, this all really should be done at the block layer so other > io-submitting-paths can benefit from it. > > IOW, maybe "the sort queue is the submission queue" wasn't a good idea.
Even if has not effect on the actual I/O patters it has a massive benefit for the filesystem. When probing delalloc/unwritten space at least XFS does try to convert a larger extent forward from the index, but doesn't bother to go backwards. By providing the trivial sort here we make life a lot easier for the filesystem.
In addition to that we do get better I/O patters especially with short queues as smart writepage implementatons will also submit the next few pages, which is essentially free given how the storage works. This means we already have a page cleaned before we might even submit it without sorting.
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