From 0021b7bc045e4b0b85d8c53614342aaf84ca96a5 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Tue, 31 Jul 2012 09:08:14 +0200 Subject: md: remove plug_cnt feature of plugging. This seemed like a good idea at the time, but after further thought I cannot see it making a difference other than very occasionally and testing to try to exercise the case it is most likely to help did not show any performance difference by removing it. So remove the counting of active plugs and allow 'pending writes' to be activated at any time, not just when no plugs are active. This is only relevant when there is a write-intent bitmap, and the updating of the bitmap will likely introduce enough delay that the single-threading of bitmap updates will be enough to collect large numbers of updates together. Removing this will make it easier to centralise the unplug code, and will clear the other for other unplug enhancements which have a measurable effect. Signed-off-by: NeilBrown Signed-off-by: Jens Axboe --- drivers/md/md.c | 5 +---- drivers/md/md.h | 3 --- drivers/md/raid1.c | 3 +-- drivers/md/raid10.c | 3 +-- drivers/md/raid5.c | 5 ++--- 5 files changed, 5 insertions(+), 14 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index d5ab4493c8be..34381172a947 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -514,8 +514,7 @@ struct md_plug_cb { static void plugger_unplug(struct blk_plug_cb *cb) { struct md_plug_cb *mdcb = container_of(cb, struct md_plug_cb, cb); - if (atomic_dec_and_test(&mdcb->mddev->plug_cnt)) - md_wakeup_thread(mdcb->mddev->thread); + md_wakeup_thread(mdcb->mddev->thread); kfree(mdcb); } @@ -548,7 +547,6 @@ int mddev_check_plugged(struct mddev *mddev) mdcb->mddev = mddev; mdcb->cb.callback = plugger_unplug; - atomic_inc(&mddev->plug_cnt); list_add(&mdcb->cb.list, &plug->cb_list); return 1; } @@ -602,7 +600,6 @@ void mddev_init(struct mddev *mddev) atomic_set(&mddev->active, 1); atomic_set(&mddev->openers, 0); atomic_set(&mddev->active_io, 0); - atomic_set(&mddev->plug_cnt, 0); spin_lock_init(&mddev->write_lock); atomic_set(&mddev->flush_pending, 0); init_waitqueue_head(&mddev->sb_wait); diff --git a/drivers/md/md.h b/drivers/md/md.h index 7b4a3c318cae..91786c46b85c 100644 --- a/drivers/md/md.h +++ b/drivers/md/md.h @@ -266,9 +266,6 @@ struct mddev { int new_chunk_sectors; int reshape_backwards; - atomic_t plug_cnt; /* If device is expecting - * more bios soon. - */ struct md_thread *thread; /* management thread */ struct md_thread *sync_thread; /* doing resync or reconstruct */ sector_t curr_resync; /* last block scheduled */ diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index cacd008d6864..36a8fc059ac3 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -2173,8 +2173,7 @@ static void raid1d(struct mddev *mddev) blk_start_plug(&plug); for (;;) { - if (atomic_read(&mddev->plug_cnt) == 0) - flush_pending_writes(conf); + flush_pending_writes(conf); spin_lock_irqsave(&conf->device_lock, flags); if (list_empty(head)) { diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index 8da6282254c3..5d33603a497d 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -2660,8 +2660,7 @@ static void raid10d(struct mddev *mddev) blk_start_plug(&plug); for (;;) { - if (atomic_read(&mddev->plug_cnt) == 0) - flush_pending_writes(conf); + flush_pending_writes(conf); spin_lock_irqsave(&conf->device_lock, flags); if (list_empty(head)) { diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 04348d76bb30..bde9da2baa39 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -4543,7 +4543,7 @@ static void raid5d(struct mddev *mddev) while (1) { struct bio *bio; - if (atomic_read(&mddev->plug_cnt) == 0 && + if ( !list_empty(&conf->bitmap_list)) { /* Now is a good time to flush some bitmap updates */ conf->seq_flush++; @@ -4553,8 +4553,7 @@ static void raid5d(struct mddev *mddev) conf->seq_write = conf->seq_flush; activate_bit_delay(conf); } - if (atomic_read(&mddev->plug_cnt) == 0) - raid5_activate_delayed(conf); + raid5_activate_delayed(conf); while ((bio = remove_bio_from_retry(conf))) { int ok; -- cgit v1.2.3