From d5be3fefc9e2db68eacfc7cfe265e2e860e4213f Mon Sep 17 00:00:00 2001 From: Paolo Valente Date: Fri, 4 Aug 2017 07:35:10 +0200 Subject: block,bfq: refactor device-idling logic The logic that decides whether to idle the device is scattered across three functions. Almost all of the logic is in the function bfq_bfqq_may_idle, but (1) part of the decision is made in bfq_update_idle_window, and (2) the function bfq_bfqq_must_idle may switch off idling regardless of the output of bfq_bfqq_may_idle. In addition, both bfq_update_idle_window and bfq_bfqq_must_idle make their decisions as a function of parameters that are used, for similar purposes, also in bfq_bfqq_may_idle. This commit addresses these issues by moving all the logic into bfq_bfqq_may_idle. Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe --- block/bfq-iosched.c | 117 +++++++++++++++++++++++++++------------------------- 1 file changed, 61 insertions(+), 56 deletions(-) (limited to 'block/bfq-iosched.c') diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 436b6ca6b1759..ccdc9e6b5df15 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -128,7 +128,7 @@ BFQ_BFQQ_FNS(busy); BFQ_BFQQ_FNS(wait_request); BFQ_BFQQ_FNS(non_blocking_wait_rq); BFQ_BFQQ_FNS(fifo_expire); -BFQ_BFQQ_FNS(idle_window); +BFQ_BFQQ_FNS(has_short_ttime); BFQ_BFQQ_FNS(sync); BFQ_BFQQ_FNS(IO_bound); BFQ_BFQQ_FNS(in_large_burst); @@ -731,10 +731,10 @@ bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd, unsigned int old_wr_coeff = bfqq->wr_coeff; bool busy = bfq_already_existing && bfq_bfqq_busy(bfqq); - if (bic->saved_idle_window) - bfq_mark_bfqq_idle_window(bfqq); + if (bic->saved_has_short_ttime) + bfq_mark_bfqq_has_short_ttime(bfqq); else - bfq_clear_bfqq_idle_window(bfqq); + bfq_clear_bfqq_has_short_ttime(bfqq); if (bic->saved_IO_bound) bfq_mark_bfqq_IO_bound(bfqq); @@ -2012,7 +2012,7 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq) return; bic->saved_ttime = bfqq->ttime; - bic->saved_idle_window = bfq_bfqq_idle_window(bfqq); + bic->saved_has_short_ttime = bfq_bfqq_has_short_ttime(bfqq); bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq); bic->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq); bic->was_in_burst_list = !hlist_unhashed(&bfqq->burst_list_node); @@ -3038,8 +3038,8 @@ void bfq_bfqq_expire(struct bfq_data *bfqd, } bfq_log_bfqq(bfqd, bfqq, - "expire (%d, slow %d, num_disp %d, idle_win %d)", reason, - slow, bfqq->dispatched, bfq_bfqq_idle_window(bfqq)); + "expire (%d, slow %d, num_disp %d, short_ttime %d)", reason, + slow, bfqq->dispatched, bfq_bfqq_has_short_ttime(bfqq)); /* * Increase, decrease or leave budget unchanged according to @@ -3121,6 +3121,18 @@ static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq) if (bfqd->strict_guarantees) return true; + /* + * Idling is performed only if slice_idle > 0. In addition, we + * do not idle if + * (a) bfqq is async + * (b) bfqq is in the idle io prio class: in this case we do + * not idle because we want to minimize the bandwidth that + * queues in this class can steal to higher-priority queues + */ + if (bfqd->bfq_slice_idle == 0 || !bfq_bfqq_sync(bfqq) || + bfq_class_idle(bfqq)) + return false; + /* * The next variable takes into account the cases where idling * boosts the throughput. @@ -3142,7 +3154,7 @@ static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq) */ idling_boosts_thr = !bfqd->hw_tag || (!blk_queue_nonrot(bfqd->queue) && bfq_bfqq_IO_bound(bfqq) && - bfq_bfqq_idle_window(bfqq)); + bfq_bfqq_has_short_ttime(bfqq)); /* * The value of the next variable, @@ -3313,16 +3325,13 @@ static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq) asymmetric_scenario && !bfq_bfqq_in_large_burst(bfqq); /* - * We have now all the components we need to compute the return - * value of the function, which is true only if both the following - * conditions hold: - * 1) bfqq is sync, because idling make sense only for sync queues; - * 2) idling either boosts the throughput (without issues), or - * is necessary to preserve service guarantees. + * We have now all the components we need to compute the + * return value of the function, which is true only if idling + * either boosts the throughput (without issues), or is + * necessary to preserve service guarantees. */ - return bfq_bfqq_sync(bfqq) && - (idling_boosts_thr_without_issues || - idling_needed_for_service_guarantees); + return idling_boosts_thr_without_issues || + idling_needed_for_service_guarantees; } /* @@ -3338,10 +3347,7 @@ static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq) */ static bool bfq_bfqq_must_idle(struct bfq_queue *bfqq) { - struct bfq_data *bfqd = bfqq->bfqd; - - return RB_EMPTY_ROOT(&bfqq->sort_list) && bfqd->bfq_slice_idle != 0 && - bfq_bfqq_may_idle(bfqq); + return RB_EMPTY_ROOT(&bfqq->sort_list) && bfq_bfqq_may_idle(bfqq); } /* @@ -3783,7 +3789,6 @@ bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic) case IOPRIO_CLASS_IDLE: bfqq->new_ioprio_class = IOPRIO_CLASS_IDLE; bfqq->new_ioprio = 7; - bfq_clear_bfqq_idle_window(bfqq); break; } @@ -3843,8 +3848,14 @@ static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, bfq_set_next_ioprio_data(bfqq, bic); if (is_sync) { + /* + * No need to mark as has_short_ttime if in + * idle_class, because no device idling is performed + * for queues in idle class + */ if (!bfq_class_idle(bfqq)) - bfq_mark_bfqq_idle_window(bfqq); + /* tentatively mark as has_short_ttime */ + bfq_mark_bfqq_has_short_ttime(bfqq); bfq_mark_bfqq_sync(bfqq); bfq_mark_bfqq_just_created(bfqq); } else @@ -3985,18 +3996,19 @@ bfq_update_io_seektime(struct bfq_data *bfqd, struct bfq_queue *bfqq, blk_rq_sectors(rq) < BFQQ_SECT_THR_NONROT); } -/* - * Disable idle window if the process thinks too long or seeks so much that - * it doesn't matter. - */ -static void bfq_update_idle_window(struct bfq_data *bfqd, - struct bfq_queue *bfqq, - struct bfq_io_cq *bic) +static void bfq_update_has_short_ttime(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + struct bfq_io_cq *bic) { - int enable_idle; + bool has_short_ttime = true; - /* Don't idle for async or idle io prio class. */ - if (!bfq_bfqq_sync(bfqq) || bfq_class_idle(bfqq)) + /* + * No need to update has_short_ttime if bfqq is async or in + * idle io prio class, or if bfq_slice_idle is zero, because + * no device idling is performed for bfqq in this case. + */ + if (!bfq_bfqq_sync(bfqq) || bfq_class_idle(bfqq) || + bfqd->bfq_slice_idle == 0) return; /* Idle window just restored, statistics are meaningless. */ @@ -4004,27 +4016,22 @@ static void bfq_update_idle_window(struct bfq_data *bfqd, bfqd->bfq_wr_min_idle_time)) return; - enable_idle = bfq_bfqq_idle_window(bfqq); - + /* Think time is infinite if no process is linked to + * bfqq. Otherwise check average think time to + * decide whether to mark as has_short_ttime + */ if (atomic_read(&bic->icq.ioc->active_ref) == 0 || - bfqd->bfq_slice_idle == 0 || - (bfqd->hw_tag && BFQQ_SEEKY(bfqq) && - bfqq->wr_coeff == 1)) - enable_idle = 0; - else if (bfq_sample_valid(bfqq->ttime.ttime_samples)) { - if (bfqq->ttime.ttime_mean > bfqd->bfq_slice_idle && - bfqq->wr_coeff == 1) - enable_idle = 0; - else - enable_idle = 1; - } - bfq_log_bfqq(bfqd, bfqq, "update_idle_window: enable_idle %d", - enable_idle); + (bfq_sample_valid(bfqq->ttime.ttime_samples) && + bfqq->ttime.ttime_mean > bfqd->bfq_slice_idle)) + has_short_ttime = false; + + bfq_log_bfqq(bfqd, bfqq, "update_has_short_ttime: has_short_ttime %d", + has_short_ttime); - if (enable_idle) - bfq_mark_bfqq_idle_window(bfqq); + if (has_short_ttime) + bfq_mark_bfqq_has_short_ttime(bfqq); else - bfq_clear_bfqq_idle_window(bfqq); + bfq_clear_bfqq_has_short_ttime(bfqq); } /* @@ -4040,14 +4047,12 @@ static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq, bfqq->meta_pending++; bfq_update_io_thinktime(bfqd, bfqq); + bfq_update_has_short_ttime(bfqd, bfqq, bic); bfq_update_io_seektime(bfqd, bfqq, rq); - if (bfqq->entity.service > bfq_max_budget(bfqd) / 8 || - !BFQQ_SEEKY(bfqq)) - bfq_update_idle_window(bfqd, bfqq, bic); bfq_log_bfqq(bfqd, bfqq, - "rq_enqueued: idle_window=%d (seeky %d)", - bfq_bfqq_idle_window(bfqq), BFQQ_SEEKY(bfqq)); + "rq_enqueued: has_short_ttime=%d (seeky %d)", + bfq_bfqq_has_short_ttime(bfqq), BFQQ_SEEKY(bfqq)); bfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq); -- cgit v1.2.3