Commit 749ef9f8 authored by Corrado Zoccolo's avatar Corrado Zoccolo Committed by Jens Axboe
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cfq: improve fsync performance for small files 



Fsync performance for small files achieved by cfq on high-end disks is
lower than what deadline can achieve, due to idling introduced between
the sync write happening in process context and the journal commit.

Moreover, when competing with a sequential reader, a process writing
small files and fsync-ing them is starved.

This patch fixes the two problems by:
- marking journal commits as WRITE_SYNC, so that they get the REQ_NOIDLE
  flag set,
- force all queues that have REQ_NOIDLE requests to be put in the noidle
  tree.

Having the queue associated to the fsync-ing process and the one associated
 to journal commits in the noidle tree allows:
- switching between them without idling,
- fairness vs. competing idling queues, since they will be serviced only
  after the noidle tree expires its slice.

Acked-by: default avatarVivek Goyal <vgoyal@redhat.com>
Reviewed-by: default avatarJeff Moyer <jmoyer@redhat.com>
Tested-by: default avatarJeff Moyer <jmoyer@redhat.com>
Signed-off-by: default avatarCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 6d0aed7a

block/cfq-iosched.c

+4 −14
Original line number Diff line number Diff line
@@ -216,7 +216,6 @@ struct cfq_data { 
	enum wl_type_t serving_type;

	unsigned long workload_expires;

	struct cfq_group *serving_group;

	bool noidle_tree_requires_idle;



	/*

	 * Each priority tree is sorted by next_request position.  These
@@ -2126,7 +2125,6 @@ static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg) 
	slice = max_t(unsigned, slice, CFQ_MIN_TT);

	cfq_log(cfqd, "workload slice:%d", slice);

	cfqd->workload_expires = jiffies + slice;

	cfqd->noidle_tree_requires_idle = false;

}



static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
@@ -3108,7 +3106,9 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	if (cfqq->queued[0] + cfqq->queued[1] >= 4)

		cfq_mark_cfqq_deep(cfqq);



	if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||

	if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))

		enable_idle = 0;

	else if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||

	    (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))

		enable_idle = 0;

	else if (sample_valid(cic->ttime_samples)) {
@@ -3421,16 +3421,6 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq) 
			cfq_slice_expired(cfqd, 1);

		else if (sync && cfqq_empty &&

			 !cfq_close_cooperator(cfqd, cfqq)) {

			cfqd->noidle_tree_requires_idle |=

				!(rq->cmd_flags & REQ_NOIDLE);

			/*

			 * Idling is enabled for SYNC_WORKLOAD.

			 * SYNC_NOIDLE_WORKLOAD idles at the end of the tree

			 * only if we processed at least one !REQ_NOIDLE request

			 */

			if (cfqd->serving_type == SYNC_WORKLOAD

			    || cfqd->noidle_tree_requires_idle

			    || cfqq->cfqg->nr_cfqq == 1)

			cfq_arm_slice_timer(cfqd);

		}

	}

fs/jbd/commit.c

+1 −1
Original line number Diff line number Diff line
@@ -318,7 +318,7 @@ void journal_commit_transaction(journal_t *journal) 
	int first_tag = 0;

	int tag_flag;

	int i;

	int write_op = WRITE;

	int write_op = WRITE_SYNC;



	/*

	 * First job: lock down the current transaction and wait for

fs/jbd2/commit.c

+1 −1
Original line number Diff line number Diff line
@@ -360,7 +360,7 @@ void jbd2_journal_commit_transaction(journal_t *journal) 
	int tag_bytes = journal_tag_bytes(journal);

	struct buffer_head *cbh = NULL; /* For transactional checksums */

	__u32 crc32_sum = ~0;

	int write_op = WRITE;

	int write_op = WRITE_SYNC;



	/*

	 * First job: lock down the current transaction and wait for

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