From eb2fd80f9d2c515a901599362e83bc3356fc5e97 Mon Sep 17 00:00:00 2001 From: Paolo Valente Date: Mon, 25 Jan 2021 20:02:43 +0100 Subject: block, bfq: replace mechanism for evaluating I/O intensity Some BFQ mechanisms make their decisions on a bfq_queue basing also on whether the bfq_queue is I/O bound. In this respect, the current logic for evaluating whether a bfq_queue is I/O bound is rather rough. This commits replaces this logic with a more effective one. The new logic measures the percentage of time during which a bfq_queue is active, and marks the bfq_queue as I/O bound if the latter if this percentage is above a fixed threshold. Tested-by: Jan Kara Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe --- block/bfq-iosched.c | 63 +++++++++++++++++++++++++++++++++++++---------------- block/bfq-iosched.h | 16 +++++++------- 2 files changed, 52 insertions(+), 27 deletions(-) (limited to 'block') diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index b12a416b51d7..375e35c3d2fb 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -1026,6 +1026,8 @@ bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd, bfqq->entity.new_weight = bic->saved_weight; bfqq->ttime = bic->saved_ttime; + bfqq->io_start_time = bic->saved_io_start_time; + bfqq->tot_idle_time = bic->saved_tot_idle_time; bfqq->wr_coeff = bic->saved_wr_coeff; bfqq->wr_start_at_switch_to_srt = bic->saved_wr_start_at_switch_to_srt; bfqq->last_wr_start_finish = bic->saved_last_wr_start_finish; @@ -1721,17 +1723,6 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, bfq_clear_bfqq_just_created(bfqq); - - if (!bfq_bfqq_IO_bound(bfqq)) { - if (arrived_in_time) { - bfqq->requests_within_timer++; - if (bfqq->requests_within_timer >= - bfqd->bfq_requests_within_timer) - bfq_mark_bfqq_IO_bound(bfqq); - } else - bfqq->requests_within_timer = 0; - } - if (bfqd->low_latency) { if (unlikely(time_is_after_jiffies(bfqq->split_time))) /* wraparound */ @@ -1865,6 +1856,36 @@ static void bfq_reset_inject_limit(struct bfq_data *bfqd, bfqq->decrease_time_jif = jiffies; } +static void bfq_update_io_intensity(struct bfq_queue *bfqq, u64 now_ns) +{ + u64 tot_io_time = now_ns - bfqq->io_start_time; + + if (RB_EMPTY_ROOT(&bfqq->sort_list) && bfqq->dispatched == 0) + bfqq->tot_idle_time += + now_ns - bfqq->ttime.last_end_request; + + if (unlikely(bfq_bfqq_just_created(bfqq))) + return; + + /* + * Must be busy for at least about 80% of the time to be + * considered I/O bound. + */ + if (bfqq->tot_idle_time * 5 > tot_io_time) + bfq_clear_bfqq_IO_bound(bfqq); + else + bfq_mark_bfqq_IO_bound(bfqq); + + /* + * Keep an observation window of at most 200 ms in the past + * from now. + */ + if (tot_io_time > 200 * NSEC_PER_MSEC) { + bfqq->io_start_time = now_ns - (tot_io_time>>1); + bfqq->tot_idle_time >>= 1; + } +} + static void bfq_add_request(struct request *rq) { struct bfq_queue *bfqq = RQ_BFQQ(rq); @@ -1872,6 +1893,7 @@ static void bfq_add_request(struct request *rq) struct request *next_rq, *prev; unsigned int old_wr_coeff = bfqq->wr_coeff; bool interactive = false; + u64 now_ns = ktime_get_ns(); bfq_log_bfqq(bfqd, bfqq, "add_request %d", rq_is_sync(rq)); bfqq->queued[rq_is_sync(rq)]++; @@ -1934,7 +1956,7 @@ static void bfq_add_request(struct request *rq) */ if (bfqd->last_completed_rq_bfqq && !bfq_bfqq_has_short_ttime(bfqq) && - ktime_get_ns() - bfqd->last_completion < + now_ns - bfqd->last_completion < 4 * NSEC_PER_MSEC) { if (bfqd->last_completed_rq_bfqq != bfqq && bfqd->last_completed_rq_bfqq != @@ -2051,6 +2073,9 @@ static void bfq_add_request(struct request *rq) } } + if (bfq_bfqq_sync(bfqq)) + bfq_update_io_intensity(bfqq, now_ns); + elv_rb_add(&bfqq->sort_list, rq); /* @@ -2712,6 +2737,8 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq) bic->saved_ttime = bfqq->ttime; bic->saved_has_short_ttime = bfq_bfqq_has_short_ttime(bfqq); bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq); + bic->saved_io_start_time = bfqq->io_start_time; + bic->saved_tot_idle_time = bfqq->tot_idle_time; bic->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq); bic->was_in_burst_list = !hlist_unhashed(&bfqq->burst_list_node); if (unlikely(bfq_bfqq_just_created(bfqq) && @@ -3979,10 +4006,6 @@ void bfq_bfqq_expire(struct bfq_data *bfqd, bfq_bfqq_budget_left(bfqq) >= entity->budget / 3))) bfq_bfqq_charge_time(bfqd, bfqq, delta); - if (reason == BFQQE_TOO_IDLE && - entity->service <= 2 * entity->budget / 10) - bfq_clear_bfqq_IO_bound(bfqq); - if (bfqd->low_latency && bfqq->wr_coeff == 1) bfqq->last_wr_start_finish = jiffies; @@ -5085,6 +5108,8 @@ static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio) static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, struct bfq_io_cq *bic, pid_t pid, int is_sync) { + u64 now_ns = ktime_get_ns(); + RB_CLEAR_NODE(&bfqq->entity.rb_node); INIT_LIST_HEAD(&bfqq->fifo); INIT_HLIST_NODE(&bfqq->burst_list_node); @@ -5112,7 +5137,9 @@ static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, bfq_clear_bfqq_sync(bfqq); /* set end request to minus infinity from now */ - bfqq->ttime.last_end_request = ktime_get_ns() + 1; + bfqq->ttime.last_end_request = now_ns + 1; + + bfqq->io_start_time = now_ns; bfq_mark_bfqq_IO_bound(bfqq); @@ -6524,8 +6551,6 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e) bfqd->bfq_slice_idle = bfq_slice_idle; bfqd->bfq_timeout = bfq_timeout; - bfqd->bfq_requests_within_timer = 120; - bfqd->bfq_large_burst_thresh = 8; bfqd->bfq_burst_interval = msecs_to_jiffies(180); diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 703895224562..c913b06016b3 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -291,6 +291,11 @@ struct bfq_queue { /* associated @bfq_ttime struct */ struct bfq_ttime ttime; + /* when bfqq started to do I/O within the last observation window */ + u64 io_start_time; + /* how long bfqq has remained empty during the last observ. window */ + u64 tot_idle_time; + /* bit vector: a 1 for each seeky requests in history */ u32 seek_history; @@ -407,6 +412,9 @@ struct bfq_io_cq { */ bool saved_IO_bound; + u64 saved_io_start_time; + u64 saved_tot_idle_time; + /* * Same purpose as the previous fields for the value of the * field keeping the queue's belonging to a large burst @@ -641,14 +649,6 @@ struct bfq_data { */ unsigned int bfq_timeout; - /* - * Number of consecutive requests that must be issued within - * the idle time slice to set again idling to a queue which - * was marked as non-I/O-bound (see the definition of the - * IO_bound flag for further details). - */ - unsigned int bfq_requests_within_timer; - /* * Force device idling whenever needed to provide accurate * service guarantees, without caring about throughput -- cgit v1.2.3