From ede7dc7fa0af619afc08995776eadb9ff3b0a711 Mon Sep 17 00:00:00 2001 From: Harshad Shirwadkar Date: Thu, 5 Nov 2020 19:58:54 -0800 Subject: jbd2: rename j_maxlen to j_total_len and add jbd2_journal_max_txn_bufs The on-disk superblock field sb->s_maxlen represents the total size of the journal including the fast commit area and is no more the max number of blocks available for a transaction. The maximum number of blocks available to a transaction is reduced by the number of fast commit blocks. So, this patch renames j_maxlen to j_total_len to better represent its intent. Also, it adds a function to calculate max number of bufs available for a transaction. Suggested-by: Jan Kara Signed-off-by: Harshad Shirwadkar Link: https://lore.kernel.org/r/20201106035911.1942128-6-harshadshirwadkar@gmail.com Signed-off-by: Theodore Ts'o --- fs/jbd2/commit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/jbd2/commit.c') diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index fa688e163a80..ec516490cb35 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -801,7 +801,7 @@ start_journal_io: if (first_block < journal->j_tail) freed += journal->j_last - journal->j_first; /* Update tail only if we free significant amount of space */ - if (freed < journal->j_maxlen / 4) + if (freed < jbd2_journal_get_max_txn_bufs(journal)) update_tail = 0; } J_ASSERT(commit_transaction->t_state == T_COMMIT); -- cgit v1.2.3 From cc80586a57f704f806b9a1b99a21cd07e37dbedc Mon Sep 17 00:00:00 2001 From: Harshad Shirwadkar Date: Thu, 5 Nov 2020 19:58:59 -0800 Subject: 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: Jan Kara Signed-off-by: Harshad Shirwadkar Link: https://lore.kernel.org/r/20201106035911.1942128-11-harshadshirwadkar@gmail.com Signed-off-by: Theodore Ts'o --- fs/jbd2/commit.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'fs/jbd2/commit.c') diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index ec516490cb35..b121d7d434c6 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -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); -- cgit v1.2.3