Commit 895e3c5c authored Jul 31, 2012 by majianpeng Committed by NeilBrown Jul 31, 2012

md/raid5: For odirect-write performance, do not set STRIPE_PREREAD_ACTIVE.



'sync' writes set both REQ_SYNC and REQ_NOIDLE.
O_DIRECT writes set REQ_SYNC but not REQ_NOIDLE.

We currently assume that a REQ_SYNC request will not be followed by
more requests and so set STRIPE_PREREAD_ACTIVE to expedite the
request.
This is appropriate for sync requests, but not for O_DIRECT requests.

So make the setting of STRIPE_PREREAD_ACTIVE conditional on REQ_NOIDLE
rather than REQ_SYNC.  This is consistent with the documented meaning
of REQ_NOIDLE:

        __REQ_NOIDLE,           /* don't anticipate more IO after this one */

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

parent b7219ccb

drivers/md/raid5.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -4135,7 +4135,7 @@ static void make_request(struct mddev mddev, struct bio bi)
		finish_wait(&conf->wait_for_overlap, &w);
		set_bit(STRIPE_HANDLE, &sh->state);
		clear_bit(STRIPE_DELAYED, &sh->state);
		if ((bi->bi_rw & REQ_SYNC) &&
		if ((bi->bi_rw & REQ_NOIDLE) &&
		!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
		atomic_inc(&conf->preread_active_stripes);
		mddev_check_plugged(mddev);

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