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jbd: don't wake kjournald unnecessarily

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
commit has already been requested for commit.

commit d9b0193 "jbd: 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>
Signed-off-by: Jan Kara <jack@suse.cz>
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1 parent b719f43 commit 7e2fb2d7e6a3094473f101ae33dd6431ae6d2ed1 Eric Sandeen committed with jankara Dec 18, 2012
Showing with 2 additions and 1 deletion.
  1. +2 −1 fs/jbd/journal.c
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@@ -446,7 +446,8 @@ int __log_start_commit(journal_t *journal, tid_t target)
* currently running transaction (if it exists). Otherwise,
* the target tid must be an old one.
*/
- if (journal->j_running_transaction &&
+ if (journal->j_commit_request != target &&
+ journal->j_running_transaction &&
journal->j_running_transaction->t_tid == target) {
/*
* We want a new commit: OK, mark the request and wakeup the

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