On Mon 20-05-24 21:18:31, Zhang Yi wrote:
> From: Zhang Yi <[email protected]>
>
> jbd2_transaction_committed() is used to check whether a transaction with
> the given tid has already committed, it holds j_state_lock in read mode
> and check the tid of current running transaction and committing
> transaction, but holding the j_state_lock is expensive.
>
> We have already stored the sequence number of the most recently
> committed transaction in journal t->j_commit_sequence, we could do this
> check by comparing it with the given tid instead. If the given tid isn't
> smaller than j_commit_sequence, we can ensure that the given transaction
> has been committed. That way we could drop the expensive lock and
> achieve about 10% ~ 20% performance gains in concurrent DIOs on may
> virtual machine with 100G ramdisk.
>
> fio -filename=/mnt/foo -direct=1 -iodepth=10 -rw=$rw -ioengine=libaio \
> -bs=4k -size=10G -numjobs=10 -runtime=60 -overwrite=1 -name=test \
> -group_reporting
>
> Before:
> overwrite IOPS=88.2k, BW=344MiB/s
> read IOPS=95.7k, BW=374MiB/s
> rand overwrite IOPS=98.7k, BW=386MiB/s
> randread IOPS=102k, BW=397MiB/s
>
> After:
> overwrite IOPS=105k, BW=410MiB/s
> read IOPS=112k, BW=436MiB/s
> rand overwrite IOPS=104k, BW=404MiB/s
> randread IOPS=111k, BW=432MiB/s
>
> CC: Dave Chinner <[email protected]>
> Suggested-by: Dave Chinner <[email protected]>
> Link: https://lore.kernel.org/linux-ext4/[email protected]/
> Signed-off-by: Zhang Yi <[email protected]>
Thanks! The patch looks good. Feel free to add:
Reviewed-by: Jan Kara <[email protected]>
Honza
> ---
> v1->v2:
> - Add READ_ONCE and WRITE_ONCE to access ->j_commit_sequence
> concurrently.
> - Keep the jbd2_transaction_committed() helper.
>
> fs/jbd2/commit.c | 2 +-
> fs/jbd2/journal.c | 12 +-----------
> 2 files changed, 2 insertions(+), 12 deletions(-)
>
> diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
> index 5e122586e06e..8244cab17688 100644
> --- a/fs/jbd2/commit.c
> +++ b/fs/jbd2/commit.c
> @@ -1108,7 +1108,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
>
> commit_transaction->t_state = T_COMMIT_CALLBACK;
> J_ASSERT(commit_transaction == journal->j_committing_transaction);
> - journal->j_commit_sequence = commit_transaction->t_tid;
> + WRITE_ONCE(journal->j_commit_sequence, commit_transaction->t_tid);
> journal->j_committing_transaction = NULL;
> commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
>
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index b6c114c11b97..cc586e3c4ee1 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -789,17 +789,7 @@ EXPORT_SYMBOL(jbd2_fc_end_commit_fallback);
> /* Return 1 when transaction with given tid has already committed. */
> int jbd2_transaction_committed(journal_t *journal, tid_t tid)
> {
> - int ret = 1;
> -
> - read_lock(&journal->j_state_lock);
> - if (journal->j_running_transaction &&
> - journal->j_running_transaction->t_tid == tid)
> - ret = 0;
> - if (journal->j_committing_transaction &&
> - journal->j_committing_transaction->t_tid == tid)
> - ret = 0;
> - read_unlock(&journal->j_state_lock);
> - return ret;
> + return tid_geq(READ_ONCE(journal->j_commit_sequence), tid);
> }
> EXPORT_SYMBOL(jbd2_transaction_committed);
>
> --
> 2.39.2
>
--
Jan Kara <[email protected]>
SUSE Labs, CR