From: Arianna Avanzini <[email protected]> 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 <[email protected]> Signed-off-by: Paolo Valente <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
