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author | Kent Overstreet <kmo@daterainc.com> | 2013-09-23 23:17:31 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-09-24 14:41:43 -0700 |
commit | c2a4f3183a1248f615a695fbd8905da55ad11bba (patch) | |
tree | 51233866301869506c0728c812fe3668ae1e94ce /drivers/md/bcache/writeback.c | |
parent | 61cbd250f867f98bb4738000afc6002d6f2b14bd (diff) | |
download | op-kernel-dev-c2a4f3183a1248f615a695fbd8905da55ad11bba.zip op-kernel-dev-c2a4f3183a1248f615a695fbd8905da55ad11bba.tar.gz |
bcache: Fix a writeback performance regression
Background writeback works by scanning the btree for dirty data and
adding those keys into a fixed size buffer, then for each dirty key in
the keybuf writing it to the backing device.
When read_dirty() finishes and it's time to scan for more dirty data, we
need to wait for the outstanding writeback IO to finish - they still
take up slots in the keybuf (so that foreground writes can check for
them to avoid races) - without that wait, we'll continually rescan when
we'll be able to add at most a key or two to the keybuf, and that takes
locks that starves foreground IO. Doh.
Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: linux-stable <stable@vger.kernel.org> # >= v3.10
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/md/bcache/writeback.c')
-rw-r--r-- | drivers/md/bcache/writeback.c | 43 |
1 files changed, 21 insertions, 22 deletions
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c index 22cbff5..27ac519 100644 --- a/drivers/md/bcache/writeback.c +++ b/drivers/md/bcache/writeback.c @@ -94,11 +94,15 @@ static void update_writeback_rate(struct work_struct *work) static unsigned writeback_delay(struct cached_dev *dc, unsigned sectors) { + uint64_t ret; + if (atomic_read(&dc->disk.detaching) || !dc->writeback_percent) return 0; - return bch_next_delay(&dc->writeback_rate, sectors * 10000000ULL); + ret = bch_next_delay(&dc->writeback_rate, sectors * 10000000ULL); + + return min_t(uint64_t, ret, HZ); } /* Background writeback */ @@ -208,7 +212,7 @@ normal_refill: up_write(&dc->writeback_lock); - ratelimit_reset(&dc->writeback_rate); + bch_ratelimit_reset(&dc->writeback_rate); /* Punt to workqueue only so we don't recurse and blow the stack */ continue_at(cl, read_dirty, dirty_wq); @@ -318,9 +322,7 @@ static void write_dirty_finish(struct closure *cl) } bch_keybuf_del(&dc->writeback_keys, w); - atomic_dec_bug(&dc->in_flight); - - closure_wake_up(&dc->writeback_wait); + up(&dc->in_flight); closure_return_with_destructor(cl, dirty_io_destructor); } @@ -349,7 +351,7 @@ static void write_dirty(struct closure *cl) closure_bio_submit(&io->bio, cl, &io->dc->disk); - continue_at(cl, write_dirty_finish, dirty_wq); + continue_at(cl, write_dirty_finish, system_wq); } static void read_dirty_endio(struct bio *bio, int error) @@ -369,7 +371,7 @@ static void read_dirty_submit(struct closure *cl) closure_bio_submit(&io->bio, cl, &io->dc->disk); - continue_at(cl, write_dirty, dirty_wq); + continue_at(cl, write_dirty, system_wq); } static void read_dirty(struct closure *cl) @@ -394,12 +396,9 @@ static void read_dirty(struct closure *cl) if (delay > 0 && (KEY_START(&w->key) != dc->last_read || - jiffies_to_msecs(delay) > 50)) { - w->private = NULL; - - closure_delay(&dc->writeback, delay); - continue_at(cl, read_dirty, dirty_wq); - } + jiffies_to_msecs(delay) > 50)) + while (delay) + delay = schedule_timeout(delay); dc->last_read = KEY_OFFSET(&w->key); @@ -424,15 +423,10 @@ static void read_dirty(struct closure *cl) trace_bcache_writeback(&w->key); - closure_call(&io->cl, read_dirty_submit, NULL, &dc->disk.cl); + down(&dc->in_flight); + closure_call(&io->cl, read_dirty_submit, NULL, cl); delay = writeback_delay(dc, KEY_SIZE(&w->key)); - - atomic_inc(&dc->in_flight); - - if (!closure_wait_event(&dc->writeback_wait, cl, - atomic_read(&dc->in_flight) < 64)) - continue_at(cl, read_dirty, dirty_wq); } if (0) { @@ -442,7 +436,11 @@ err: bch_keybuf_del(&dc->writeback_keys, w); } - refill_dirty(cl); + /* + * Wait for outstanding writeback IOs to finish (and keybuf slots to be + * freed) before refilling again + */ + continue_at(cl, refill_dirty, dirty_wq); } /* Init */ @@ -484,6 +482,7 @@ void bch_sectors_dirty_init(struct cached_dev *dc) void bch_cached_dev_writeback_init(struct cached_dev *dc) { + sema_init(&dc->in_flight, 64); closure_init_unlocked(&dc->writeback); init_rwsem(&dc->writeback_lock); @@ -513,7 +512,7 @@ void bch_writeback_exit(void) int __init bch_writeback_init(void) { - dirty_wq = create_singlethread_workqueue("bcache_writeback"); + dirty_wq = create_workqueue("bcache_writeback"); if (!dirty_wq) return -ENOMEM; |