From: Theodore Ts'o Subject: [PATCH 1/2] jbd2: don't wake kjournald unnecessarily Date: Wed, 30 Jan 2013 00:39:28 -0500 Message-ID: <1359524369-31234-1-git-send-email-tytso@mit.edu> References: <20130130052658.GE25006@thunk.org> Cc: Theodore Ts'o , Eric Sandeen , Sedat Dilek , mszeredi@suse.cz To: Ext4 Developers List Return-path: Received: from li9-11.members.linode.com ([67.18.176.11]:46154 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751220Ab3A3Fji (ORCPT ); Wed, 30 Jan 2013 00:39:38 -0500 In-Reply-To: <20130130052658.GE25006@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: 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. Reported-by: Eric Sandeen Signed-off-by: "Theodore Ts'o" Cc: Eric Sandeen Cc: Sedat Dilek Cc: mszeredi@suse.cz --- Eric, I think this might be clearer than the patch which you proposed; what do you think? fs/jbd2/journal.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index dbf41f9..1a80e31 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -513,6 +513,10 @@ int __jbd2_log_space_left(journal_t *journal) */ 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 * currently running transaction (if it exists). Otherwise, -- 1.7.12.rc0.22.gcdd159b