Messages in this thread | | | From | Bodo Eggert <> | Subject | Re: [PATCH] dm-snapshot: poor copy-on-write performance due to I/O reordering | Date | Wed, 17 Sep 2008 17:47:50 +0200 |
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Kazuo Ito <ito.kazuo@oss.ntt.co.jp> wrote:
> Write throughput to LVM snapshot origin volume is an order > of magnitude slower than those to LV without snapshots or > snapshot target volumes, especially in the case of sequential > writes with O_SYNC on. > > The following patch originally written by Kevin Jamieson and > Jan Blunck and slightly modified for the current RCs by myself > tries to improve the performance by modifying the behaviour > of kcopyd, so that it pushes back an I/O job to the head of > the job queue instead of the tail as process_jobs() currently > does when it has to wait for free pages. This way, write > requests aren't shuffled to cause extra seeks.
Did you check for starvation problems, too?
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