From: Paolo Valente <paolo.valente@linaro.org>
To: Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>
Cc: Fabio Checconi <fchecconi@gmail.com>,
Arianna Avanzini <avanzini.arianna@gmail.com>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
ulf.hansson@linaro.org, linus.walleij@linaro.org,
broonie@kernel.org, Paolo Valente <paolo.valente@linaro.org>
Subject: [PATCH RFC V8 06/22] block, cfq: get rid of queue preemption
Date: Wed, 27 Jul 2016 18:13:22 +0200 [thread overview]
Message-ID: <1469636018-31247-7-git-send-email-paolo.valente@linaro.org> (raw)
In-Reply-To: <1469636018-31247-1-git-send-email-paolo.valente@linaro.org>
From: Arianna Avanzini <avanzini.arianna@gmail.com>
CFQ implements a request-triggered queue preemption, based on the
priority class of the queues, and aimed at reducing latencies. There
is no such preemption in BFQ, where a low latency is guaranteed only
by the overall request-scheduling policy.
Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
---
block/cfq-iosched.c | 99 +----------------------------------------------------
1 file changed, 1 insertion(+), 98 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index fab01e2..174dc94 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1069,8 +1069,7 @@ static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
}
/*
- * Get next queue for service. Unless we have a queue preemption,
- * we'll simply select the first cfqq in the service tree.
+ * Get next queue for service.
*/
static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
{
@@ -1929,93 +1928,6 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
}
/*
- * Check if new_cfqq should preempt the currently active queue. Return 0 for
- * no or if we aren't sure, a 1 will cause a preempt.
- */
-static bool
-cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
- struct request *rq)
-{
- struct cfq_queue *cfqq;
-
- cfqq = cfqd->active_queue;
- if (!cfqq)
- return false;
-
- if (cfq_class_idle(new_cfqq))
- return false;
-
- if (cfq_class_idle(cfqq))
- return true;
-
- /*
- * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
- */
- if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
- return false;
-
- /*
- * if the new request is sync, but the currently running queue is
- * not, let the sync request have priority.
- */
- if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
- return true;
-
- if (cfq_slice_used(cfqq))
- return true;
-
- /*
- * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
- */
- if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
- return true;
-
- WARN_ON_ONCE(cfqq->ioprio_class != new_cfqq->ioprio_class);
- /* Allow preemption only if we are idling on sync-noidle tree */
- if (cfqd->serving_wl_type == SYNC_NOIDLE_WORKLOAD &&
- cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
- RB_EMPTY_ROOT(&cfqq->sort_list))
- return true;
-
- /*
- * So both queues are sync. Let the new request get disk time if
- * it's a metadata request and the current queue is doing regular IO.
- */
- if ((rq->cmd_flags & REQ_PRIO) && !cfqq->prio_pending)
- return true;
-
- /* An idle queue should not be idle now for some reason */
- if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))
- return true;
-
- if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
- return false;
-
- return false;
-}
-
-/*
- * cfqq preempts the active queue. if we allowed preempt with no slice left,
- * let it have half of its nominal slice.
- */
-static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
-{
- cfq_log_cfqq(cfqd, cfqq, "preempt");
- cfq_slice_expired(cfqd, 1);
-
- /*
- * Put the new queue at the front of the of the current list,
- * so we know that it will be selected next.
- */
- BUG_ON(!cfq_cfqq_on_rr(cfqq));
-
- cfq_service_tree_add(cfqd, cfqq, 1);
-
- cfqq->slice_end = 0;
- cfq_mark_cfqq_slice_new(cfqq);
-}
-
-/*
* Called when a new fs request (rq) is added (to cfqq). Check if there's
* something we should do about it
*/
@@ -2055,15 +1967,6 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
} else
cfq_mark_cfqq_must_dispatch(cfqq);
}
- } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
- /*
- * not the active queue - expire current slice if it is
- * idle and has expired it's mean thinktime or this new queue
- * has some old slice time left and is of higher priority or
- * this new queue is RT and the current one is BE
- */
- cfq_preempt_queue(cfqd, cfqq);
- __blk_run_queue(cfqd->queue);
}
}
--
1.9.1
next prev parent reply other threads:[~2016-07-27 16:14 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-01 22:12 [PATCH RFC 00/22] Replace the CFQ I/O Scheduler with BFQ Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 01/22] block, cfq: remove queue merging for close cooperators Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 02/22] block, cfq: remove close-based preemption Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 03/22] block, cfq: remove deep seek queues logic Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 04/22] block, cfq: remove SSD-related logic Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 05/22] block, cfq: get rid of hierarchical support Paolo Valente
2016-02-10 23:04 ` Tejun Heo
2016-02-01 22:12 ` [PATCH RFC 06/22] block, cfq: get rid of queue preemption Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 07/22] block, cfq: get rid of workload type Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 08/22] block, cfq: get rid of latency tunables Paolo Valente
2016-02-10 23:05 ` Tejun Heo
2016-02-01 22:12 ` [PATCH RFC 09/22] block, cfq: replace CFQ with the BFQ-v0 I/O scheduler Paolo Valente
2016-02-11 22:22 ` Tejun Heo
2016-02-12 0:35 ` Mark Brown
2016-02-17 15:57 ` Tejun Heo
2016-02-17 16:02 ` Mark Brown
2016-02-17 17:04 ` Tejun Heo
2016-02-17 18:13 ` Jonathan Corbet
2016-02-17 19:45 ` Tejun Heo
2016-02-17 19:56 ` Jonathan Corbet
2016-02-17 20:14 ` Tejun Heo
2016-02-17 9:02 ` Paolo Valente
2016-02-17 17:02 ` Tejun Heo
2016-02-20 10:23 ` Paolo Valente
2016-02-20 11:02 ` Paolo Valente
2016-03-01 18:46 ` Tejun Heo
2016-03-04 17:29 ` Linus Walleij
2016-03-04 17:39 ` Christoph Hellwig
2016-03-04 18:10 ` Austin S. Hemmelgarn
2016-03-11 11:16 ` Christoph Hellwig
2016-03-11 13:38 ` Austin S. Hemmelgarn
2016-03-05 12:18 ` Linus Walleij
2016-03-11 11:17 ` Christoph Hellwig
2016-03-11 11:24 ` Nikolay Borisov
2016-03-11 11:49 ` Christoph Hellwig
2016-03-11 14:53 ` Linus Walleij
2016-03-09 6:55 ` Paolo Valente
2016-04-13 19:54 ` Tejun Heo
2016-04-14 5:03 ` Mark Brown
2016-03-09 6:34 ` Paolo Valente
2016-04-13 20:41 ` Tejun Heo
2016-04-14 10:23 ` Paolo Valente
2016-04-14 16:29 ` Tejun Heo
2016-04-15 14:20 ` Paolo Valente
2016-04-15 15:08 ` Tejun Heo
2016-04-15 16:17 ` Paolo Valente
2016-04-15 19:29 ` Tejun Heo
2016-04-15 22:08 ` Paolo Valente
2016-04-15 22:45 ` Tejun Heo
2016-04-16 6:03 ` Paolo Valente
2016-04-15 14:49 ` Linus Walleij
2016-02-01 22:12 ` [PATCH RFC 10/22] block, bfq: add full hierarchical scheduling and cgroups support Paolo Valente
2016-02-11 22:28 ` Tejun Heo
2016-02-17 9:07 ` Paolo Valente
2016-02-17 17:14 ` Tejun Heo
2016-02-17 17:45 ` Tejun Heo
2016-04-20 9:32 ` Paolo
2016-04-22 18:13 ` Tejun Heo
2016-04-22 18:19 ` Paolo Valente
2016-04-22 18:41 ` Tejun Heo
2016-04-22 19:05 ` Paolo Valente
2016-04-22 19:32 ` Tejun Heo
2016-04-23 7:07 ` Paolo Valente
2016-04-25 19:24 ` Tejun Heo
2016-04-25 20:30 ` Paolo
2016-05-06 20:20 ` Paolo Valente
2016-05-12 13:11 ` Paolo
2016-07-27 16:13 ` [PATCH RFC V8 00/22] Replace the CFQ I/O Scheduler with BFQ Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 01/22] block, cfq: remove queue merging for close cooperators Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 02/22] block, cfq: remove close-based preemption Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 03/22] block, cfq: remove deep seek queues logic Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 04/22] block, cfq: remove SSD-related logic Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 05/22] block, cfq: get rid of hierarchical support Paolo Valente
2016-07-27 16:13 ` Paolo Valente [this message]
2016-07-27 16:13 ` [PATCH RFC V8 07/22] block, cfq: get rid of workload type Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 08/22] block, cfq: get rid of latency tunables Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 09/22] block, cfq: replace CFQ with the BFQ-v0 I/O scheduler Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 10/22] block, bfq: add full hierarchical scheduling and cgroups support Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 11/22] block, bfq: improve throughput boosting Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 12/22] block, bfq: modify the peak-rate estimator Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 13/22] block, bfq: add more fairness with writes and slow processes Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 14/22] block, bfq: improve responsiveness Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 15/22] block, bfq: reduce I/O latency for soft real-time applications Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 16/22] block, bfq: preserve a low latency also with NCQ-capable drives Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 17/22] block, bfq: reduce latency during request-pool saturation Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 18/22] block, bfq: add Early Queue Merge (EQM) Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 19/22] block, bfq: reduce idling only in symmetric scenarios Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 20/22] block, bfq: boost the throughput on NCQ-capable flash-based devices Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 21/22] block, bfq: boost the throughput with random I/O on NCQ-capable HDDs Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 22/22] block, bfq: handle bursts of queue activations Paolo Valente
2016-07-28 16:50 ` [PATCH RFC V8 00/22] Replace the CFQ I/O Scheduler with BFQ Paolo
2016-02-01 22:12 ` [PATCH RFC 11/22] block, bfq: improve throughput boosting Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 12/22] block, bfq: modify the peak-rate estimator Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 13/22] block, bfq: add more fairness to boost throughput and reduce latency Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 14/22] block, bfq: improve responsiveness Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 15/22] block, bfq: reduce I/O latency for soft real-time applications Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 16/22] block, bfq: preserve a low latency also with NCQ-capable drives Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 17/22] block, bfq: reduce latency during request-pool saturation Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 18/22] block, bfq: add Early Queue Merge (EQM) Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 19/22] block, bfq: reduce idling only in symmetric scenarios Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 20/22] block, bfq: boost the throughput on NCQ-capable flash-based devices Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 21/22] block, bfq: boost the throughput with random I/O on NCQ-capable HDDs Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 22/22] block, bfq: handle bursts of queue activations Paolo Valente
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