[PATCH 5/8] jbd2: use WRITE_SYNC_PLUG instead of WRITE_SYNC

From: Jens Axboe
Date: Mon Apr 06 2009 - 08:49:49 EST


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@xxxxxxxxxx>
---
fs/jbd2/commit.c | 13 +++++++++----
1 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 4ea7237..073c8c3 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -138,7 +138,7 @@ static int journal_submit_commit_record(journal_t *journal,
set_buffer_ordered(bh);
barrier_done = 1;
}
- ret = submit_bh(WRITE_SYNC, bh);
+ ret = submit_bh(WRITE_SYNC_PLUG, bh);
if (barrier_done)
clear_buffer_ordered(bh);

@@ -159,7 +159,7 @@ static int journal_submit_commit_record(journal_t *journal,
lock_buffer(bh);
set_buffer_uptodate(bh);
clear_buffer_dirty(bh);
- ret = submit_bh(WRITE_SYNC, bh);
+ ret = submit_bh(WRITE_SYNC_PLUG, bh);
}
*cbh = bh;
return ret;
@@ -190,7 +190,7 @@ retry:
set_buffer_uptodate(bh);
bh->b_end_io = journal_end_buffer_io_sync;

- ret = submit_bh(WRITE_SYNC, bh);
+ ret = submit_bh(WRITE_SYNC_PLUG, bh);
if (ret) {
unlock_buffer(bh);
return ret;
@@ -402,8 +402,13 @@ void jbd2_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;
stats.u.run.rs_wait = commit_transaction->t_max_wait;
stats.u.run.rs_locked = jiffies;
stats.u.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
--
1.6.2.1.423.g442d

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