From: Tao Ma <boyu...@taobao.com>
In commit 749ef9f8423, we use WRITE_SYNC instead of WRITE in
journal_commit_transaction. It causes a much heavy burden for
the disk as now the seqenctial write can't be merged(see the blktrace below).
Given the description of that commit 749ef9f8423, the reason why
we use WRITE_SYNC is that it wants to use REQ_NOIDLE and WRITE_SYNC_PLUG
also has that flag, so use WRITE_SYNC_PLUG instead. From blktrace,
we can get that:
without the patch:
8,0 6 18 0.016058423 3342 D W 461101317 + 4 [jbd2/sda11-8]
8,0 6 19 0.016065473 3342 D W 461101321 + 4 [jbd2/sda11-8]
8,0 6 20 0.016070751 3342 D W 461101325 + 4 [jbd2/sda11-8]
8,0 6 21 0.016076180 3342 D W 461101329 + 4 [jbd2/sda11-8]
8,0 6 22 0.016081255 3342 D W 461101333 + 4 [jbd2/sda11-8]
8,0 6 23 0.016085963 3342 D W 461101337 + 4 [jbd2/sda11-8]
8,0 6 24 0.016182048 0 C W 461101317 + 4 [0]
8,0 6 25 0.016190820 0 C W 461101325 + 4 [0]
8,0 6 26 0.016193927 0 C W 461101321 + 4 [0]
8,0 6 27 0.016196532 0 C W 461101333 + 4 [0]
8,0 6 28 0.016199180 0 C W 461101337 + 4 [0]
8,0 6 29 0.016206180 0 C W 461101329 + 4 [0]
with this patch:
8,0 4 23 4.320315739 3129 D W 461101317 + 24 [jbd2/sda11-8]
8,0 4 24 4.320364518 0 C W 461101317 + 24 [0]
This only affects .37 and .38 since Jens' new plug patches are included
in .39 and the bug is removed as a side effect. But I think it is needed
anyway for the stable. And RHEL6 needs this also I guess.
Cc: sta...@kernel.org # 2.6.37 and 2.6.38
Cc: Jan Kara <j...@suse.cz>
Cc: Vivek Goyal <vgo...@redhat.com>
Cc: Jeff Moyer <jmo...@redhat.com>
Cc: Corrado Zoccolo <czocc...@gmail.com>
Cc: Jens Axboe <jax...@fusionio.com>
Signed-off-by: Tao Ma <boyu...@taobao.com>
---
fs/jbd/commit.c | 9 +--------
fs/jbd2/commit.c | 9 +--------
2 files changed, 2 insertions(+), 16 deletions(-)
diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index 34a4861..6d13df5 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -294,7 +294,7 @@ void journal_commit_transaction(journal_t *journal)
int first_tag = 0;
int tag_flag;
int i;
- int write_op = WRITE_SYNC;
+ int write_op = WRITE_SYNC_PLUG;
/*
* First job: lock down the current transaction and wait for
@@ -327,13 +327,6 @@ 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_PLUG;
spin_lock(&commit_transaction->t_handle_lock);
while (commit_transaction->t_updates) {
DEFINE_WAIT(wait);
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index f3ad159..fc3840f 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -329,7 +329,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
int tag_bytes = journal_tag_bytes(journal);
struct buffer_head *cbh = NULL; /* For transactional checksums */
__u32 crc32_sum = ~0;
- int write_op = WRITE_SYNC;
+ int write_op = WRITE_SYNC_PLUG;
/*
* First job: lock down the current transaction and wait for
@@ -363,13 +363,6 @@ void jbd2_journal_commit_transaction(journal_t *journal)
write_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_PLUG;
trace_jbd2_commit_locking(journal, commit_transaction);
stats.run.rs_wait = commit_transaction->t_max_wait;
stats.run.rs_locked = jiffies;
--
1.7.4
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