From: Arianna Avanzini <avanzini.arianna@xxxxxxxxx>
CFQ implements a heuristic to identify seeky queues experiencing large
queue depths (>= 4), and let them idle despite their seekiness. This
mechanism has no match in BFQ, where idling decisions are taken
according to a unified global strategy. In this strategy, all actions
are aimed at boosting the throughput, except for when
throughput-boosting actions would jeopardize throughput-distribution
and latency guarantees. Full details in the commits turning CFQ into
BFQ.
Signed-off-by: Arianna Avanzini <avanzini.arianna@xxxxxxxxx>
Signed-off-by: Paolo Valente <paolo.valente@xxxxxxxxxx>
---
block/cfq-iosched.c | 21 ++++-----------------
1 file changed, 4 insertions(+), 17 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 1b9fa10..870d1ba 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -411,7 +411,6 @@ enum cfqq_state_flags {
CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
CFQ_CFQQ_FLAG_sync, /* synchronous queue */
- CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */
CFQ_CFQQ_FLAG_wait_busy, /* Waiting for next request */
};
@@ -438,7 +437,6 @@ CFQ_CFQQ_FNS(idle_window);
CFQ_CFQQ_FNS(prio_changed);
CFQ_CFQQ_FNS(slice_new);
CFQ_CFQQ_FNS(sync);
-CFQ_CFQQ_FNS(deep);
CFQ_CFQQ_FNS(wait_busy);
#undef CFQ_CFQQ_FNS
@@ -3036,15 +3034,13 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
}
/*
- * This is a deep seek queue, but the device is much faster than
- * the queue can deliver, don't idle
+ * The device is much faster than the queue can deliver: don't idle
**/
if (CFQQ_SEEKY(cfqq) && cfq_cfqq_idle_window(cfqq) &&
(cfq_cfqq_slice_new(cfqq) ||
- (cfqq->slice_end - jiffies > jiffies - cfqq->slice_start))) {
- cfq_clear_cfqq_deep(cfqq);
+ (time_after(cfqq->slice_end - jiffies,
+ jiffies - cfqq->slice_start))))
cfq_clear_cfqq_idle_window(cfqq);
- }
if (cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
cfqq = NULL;
@@ -3622,14 +3618,10 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
- if (cfqq->queued[0] + cfqq->queued[1] >= 4)
- cfq_mark_cfqq_deep(cfqq);
-
if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))
enable_idle = 0;
else if (!atomic_read(&cic->icq.ioc->active_ref) ||
- !cfqd->cfq_slice_idle ||
- (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
+ !cfqd->cfq_slice_idle || CFQQ_SEEKY(cfqq))
enable_idle = 0;
else if (sample_valid(cic->ttime.ttime_samples)) {
if (cic->ttime.ttime_mean > cfqd->cfq_slice_idle)
@@ -4128,11 +4120,6 @@ static void cfq_idle_slice_timer(unsigned long data)
*/
if (!RB_EMPTY_ROOT(&cfqq->sort_list))
goto out_kick;
-
- /*
- * Queue depth flag is reset only when the idle didn't succeed
- */
- cfq_clear_cfqq_deep(cfqq);
}
expire:
cfq_slice_expired(cfqd, timed_out);
--
1.9.1
--
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