hulk inclusion category: performance bugzilla: https://gitee.com/openeuler/kernel/issues/I9QSJ5 CVE: NA

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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 david@fromorbit.com Suggested-by: Dave Chinner david@fromorbit.com Link: https://lore.kernel.org/linux-ext4/ZjILCPNZRHeazSqV@dread.disaster.area/ Signed-off-by: Zhang Yi yi.zhang@huawei.com Reviewed-by: Jan Kara jack@suse.cz --- 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 19c69229ac6e..fc4c7a2bf6d5 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);