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: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Tested-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index b9f8619..6845926 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -216,7 +216,6 @@
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 @@
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 @@
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)) {
@@ -3421,17 +3421,7 @@
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);
+ cfq_arm_slice_timer(cfqd);
}
}