Commit d868d230 authored by Zhang Yi's avatar Zhang Yi
Browse files

jbd2: speed up jbd2_transaction_committed() 

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


CVE: NA

--------------------------------

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: default avatarDave Chinner <david@fromorbit.com>
Link: https://lore.kernel.org/linux-ext4/ZjILCPNZRHeazSqV@dread.disaster.area/


Signed-off-by: default avatarZhang Yi <yi.zhang@huawei.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
parent 4da472bb

fs/jbd2/commit.c

+1 −1
Original line number Diff line number Diff line
@@ -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));

fs/jbd2/journal.c

+1 −11
Original line number Diff line number Diff line
@@ -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);