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jbd2: avoid pointless scanning of checkpoint lists 

Yuanhan has reported that when he is running fsync(2) heavy workload
creating new files over ramdisk, significant amount of time is spent in
__jbd2_journal_clean_checkpoint_list() trying to clean old transactions
(but they cannot be cleaned up because flusher hasn't yet checkpointed
those buffers). The workload can be generated by:
  fs_mark -d /fs/ram0/1 -D 2 -N 2560 -n 1000000 -L 1 -S 1 -s 4096

Reduce the amount of scanning by stopping to scan the transaction list
once we find a transaction that cannot be checkpointed. Note that this
way of cleaning is still enough to keep freeing space in the journal
after fully checkpointed transactions.

Reported-and-tested-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Jan Kara 2014-09-18 00:42:16 -04:00 committed by Theodore Ts'o
parent 844749764b
commit cc97f1a7c7
1 changed files with 18 additions and 14 deletions
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32
fs/jbd2/checkpoint.c
View File

@ -420,7 +420,6 @@ int jbd2_cleanup_journal_tail(journal_t *journal)
* Find all the written-back checkpoint buffers in the given list and
* release them.
*
* Called with the journal locked.
* Called with j_list_lock held.
* Returns number of buffers reaped (for debug)
*/
@ -440,12 +439,12 @@ static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
jh = next_jh;
next_jh = jh->b_cpnext;
ret = __try_to_free_cp_buf(jh);
if (ret) {
freed++;
if (ret == 2) {
*released = 1;
return freed;
}
if (!ret)
return freed;
freed++;
if (ret == 2) {
*released = 1;
return freed;
}
/*
* This function only frees up some memory
@ -465,7 +464,6 @@ static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
*
* Find all the written-back checkpoint buffers in the journal and release them.
*
* Called with the journal locked.
* Called with j_list_lock held.
* Returns number of buffers reaped (for debug)
*/
@ -473,7 +471,8 @@ static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
{
transaction_t *transaction, *last_transaction, *next_transaction;
int ret = 0;
int ret;
int freed = 0;
int released;
transaction = journal->j_checkpoint_transactions;
@ -485,17 +484,21 @@ int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
do {
transaction = next_transaction;
next_transaction = transaction->t_cpnext;
ret += journal_clean_one_cp_list(transaction->
ret = journal_clean_one_cp_list(transaction->
t_checkpoint_list, &released);
/*
* This function only frees up some memory if possible so we
* dont have an obligation to finish processing. Bail out if
* preemption requested:
*/
if (need_resched())
if (need_resched()) {
freed += ret;
goto out;
if (released)
}
if (released) {
freed += ret;
continue;
}
/*
* It is essential that we are as careful as in the case of
* t_checkpoint_list with removing the buffer from the list as
@ -503,11 +506,12 @@ int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
*/
ret += journal_clean_one_cp_list(transaction->
t_checkpoint_io_list, &released);
if (need_resched())
freed += ret;
if (need_resched() || !ret)
goto out;
} while (transaction != last_transaction);
out:
return ret;
return freed;
}
/*