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Subject[PATCH 4/8] jbd: use WRITE_SYNC_PLUG instead of WRITE_SYNC
Date
When you are going to be submitting several sync writes, we want to
give the IO scheduler a chance to merge some of them. Instead of
using the implicitly unplugging WRITE_SYNC variant, use WRITE_SYNC_PLUG
and rely on sync_buffer() doing the unplug when someone does a
wait_on_buffer()/lock_buffer().

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
fs/jbd/commit.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index f8077b9..a8e8513 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -351,8 +351,13 @@ void journal_commit_transaction(journal_t *journal)
spin_lock(&journal->j_state_lock);
commit_transaction->t_state = T_LOCKED;

+ /*
+ * Use plugged writes here, since we want to submit several before
+ * we unplug the device. We don't do explicit unplugging in here,
+ * instead we rely on sync_buffer() doing the unplug for us.
+ */
if (commit_transaction->t_synchronous_commit)
- write_op = WRITE_SYNC;
+ write_op = WRITE_SYNC_PLUG;
spin_lock(&commit_transaction->t_handle_lock);
while (commit_transaction->t_updates) {
DEFINE_WAIT(wait);
--
1.6.2.1.423.g442d


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