From: Jeff Moyer on
In my fsync testing, journal I/O most definitely was sync I/O, since
another process was blocked waiting for the results. By marking all
journal I/O as WRITE_SYNC, I can get better performance with CFQ.

If there is a way to mark this only for cases where it is blocking progress
in a dependent process, then that would be preferrable. Is there such a
means for determining and flagging this?

Cheers,
Jeff

Signed-off-by: Jeff Moyer <jmoyer(a)redhat.com>
---
fs/jbd2/commit.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 75716d3..a078744 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -369,7 +369,7 @@ 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;
+ int write_op = WRITE_SYNC;

/*
* First job: lock down the current transaction and wait for
--
1.6.5.2

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