Commit cc80586a authored by Harshad Shirwadkar's avatar Harshad Shirwadkar Committed by Theodore Ts'o
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jbd2: add todo for a fast commit performance optimization 



Fast commit performance can be optimized if commit thread doesn't wait
for ongoing fast commits to complete until the transaction enters
T_FLUSH state. Document this optimization.

Suggested-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarHarshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20201106035911.1942128-11-harshadshirwadkar@gmail.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 0bce577b

fs/jbd2/commit.c

+9 −0
Original line number Diff line number Diff line
@@ -450,6 +450,15 @@ void jbd2_journal_commit_transaction(journal_t *journal) 
		schedule();

		write_lock(&journal->j_state_lock);

		finish_wait(&journal->j_fc_wait, &wait);

		/*

		 * TODO: by blocking fast commits here, we are increasing

		 * fsync() latency slightly. Strictly speaking, we don't need

		 * to block fast commits until the transaction enters T_FLUSH

		 * state. So an optimization is possible where we block new fast

		 * commits here and wait for existing ones to complete

		 * just before we enter T_FLUSH. That way, the existing fast

		 * commits and this full commit can proceed parallely.

		 */

	}

	write_unlock(&journal->j_state_lock);