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Commit cc97f1a7 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
Browse files

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: default avatarYuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 84474976

fs/jbd2/checkpoint.c

+18 −14
Original line number Diff line number Diff line
@@ -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)

 */
@@ -440,13 +439,13 @@ 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) {

		if (!ret)

			return freed;

		freed++;

		if (ret == 2) {

			*released = 1;

			return freed;

		}

		}

		/*

		 * This function only frees up some memory

		 * if possible so we dont have an obligation
@@ -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;

}



/*