Commit 053f5b65 authored Jun 09, 2014 by Eivind Sarto Committed by NeilBrown Jun 10, 2014

raid5: speedup sync_request processing



The raid5 sync_request() processing calls handle_stripe() within the context of
the resync-thread.  The resync-thread issues the first set of read requests
and this adds execution latency and slows down the scheduling of the next
sync_request().
The current rebuild/resync speed of raid5 is not much faster than what
rotational HDDs can sustain.
Testing the following patch on a 6-drive array, I can increase the rebuild
speed from 100 MB/s to 175 MB/s.
The sync_request() now just sets STRIPE_HANDLE and releases the stripe.  This
creates some more parallelism between the resync-thread and raid5 kernel daemon.

Signed-off-by: Eivind Sarto <esarto@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

parent 2844dc32

drivers/md/raid5.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -5074,8 +5074,8 @@ static inline sector_t sync_request(struct mddev *mddev, sector_t sector_nr, int
		bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, still_degraded);

		set_bit(STRIPE_SYNC_REQUESTED, &sh->state);
		set_bit(STRIPE_HANDLE, &sh->state);

		handle_stripe(sh);
		release_stripe(sh);

		return STRIPE_SECTORS;

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