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jbd2: don't wake kjournald unnecessarily

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Don't send an extra wakeup to kjournald in the case where we
already have the proper target in j_commit_request, i.e. that
transaction has already been requested for commit.

commit deeeaf13 "jbd2: fix fsync() tid wraparound bug" changed
the logic leading to a wakeup, but it caused some extra wakeups
which were found to lead to a measurable performance regression.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
[tytso@mit.edu: reworked check to make it clearer]
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Eric Sandeen 2013-01-30 00:39:28 -05:00 committed by Theodore Ts'o
parent 091e26dfc1
commit e7b04ac00e
1 changed files with 4 additions and 0 deletions
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4
fs/jbd2/journal.c
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@ -513,6 +513,10 @@ int __jbd2_log_space_left(journal_t *journal)
*/ */
int __jbd2_log_start_commit(journal_t *journal, tid_t target) int __jbd2_log_start_commit(journal_t *journal, tid_t target)
{ {
/* Return if the txn has already requested to be committed */
if (journal->j_commit_request == target)
return 0;
/* /*
* The only transaction we can possibly wait upon is the * The only transaction we can possibly wait upon is the
* currently running transaction (if it exists). Otherwise, * currently running transaction (if it exists). Otherwise,