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

PATCH In review majianpeng 2 participants 2 messages Jul 16, 2012 – Jul 17, 2012 MD RAID

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majianpeng

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PATCH 2/2 raid5: For odirect-write performance, not set STRIPE_PREREAD_ACTIVE.

Using flag REQ_NOIDLE to difference odirect-write and sync_write.

Signed-off-by Jianpeng Ma <[email protected]>
---
 drivers/md/raid5.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
drivers/md/raid5.c +4 -1
index 04348d7..29edaf0 100644
@@ -4113,7 +4113,10 @@ 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) &&
+			/* Difference odirect-write between regular file
+			 * and block-device
+			 */
+			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);
Signature · 1 line
1.7.5.4
#1 lore raw
Quoted 13 lines · On Mon, 16 Jul 2012 16:33:02 +0800 majianpeng <[email protected]> wrote:

Using flag REQ_NOIDLE to difference odirect-write and sync_write.

Signed-off-by Jianpeng Ma <[email protected]>
---
 drivers/md/raid5.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
drivers/md/raid5.c +0 -0
index 04348d7..29edaf0 100644
@@ -4113,7 +4113,10 @@ static void make_request(struct mddev *mddev, struct bio * bi)
 			finish_wait(&conf->wait_for_overlap, &w);

drivers/md/raid5.c static void make_request(struct mddev *mddev, struct bio * bi) · line 4122

Quoted 10 lines
drivers/md/raid5.c +4 -1
 			set_bit(STRIPE_HANDLE, &sh->state);
 			clear_bit(STRIPE_DELAYED, &sh->state);
-			if ((bi->bi_rw & REQ_SYNC) &&
+			/* Difference odirect-write between regular file
+			 * and block-device
+			 */
+			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);

Thanks.
I've improved that patch description and remove the code comment and I don't think it is helpful.

NeilBrown

From c6e353648f062901f435f67b91e9438897d42ddf Mon Sep 17 00:00:00 2001
From: majianpeng <[email protected]>
Date: Tue, 17 Jul 2012 12:00:35 +1000
Subject: [PATCH] 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 <[email protected]>
Signed-off-by NeilBrown <[email protected]>
drivers/md/raid5.c +1 -1
index 0e4439e..ee492a8 100644
@@ -4187,7 +4187,7 @@ 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);
 			release_stripe_plug(mddev, sh);