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From: Yu Kuai <yukuai3@huawei.com>
To: <paolo.valente@linaro.org>, <axboe@kernel.dk>
Cc: <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<yukuai3@huawei.com>, <yi.zhang@huawei.com>
Subject: [PATCH 3/3] block, bfq: consider request size in bfq_asymmetric_scenario()
Date: Wed, 14 Jul 2021 17:45:29 +0800	[thread overview]
Message-ID: <20210714094529.758808-4-yukuai3@huawei.com> (raw)
In-Reply-To: <20210714094529.758808-1-yukuai3@huawei.com>

There is a special case when bfq do not need to idle when more than
one groups is active:

 1) all active queues have the same weight,
 2) all active queues have the same request size.
 3) all active queues belong to the same I/O-priority class,

Each time a request is dispatched, bfq can switch in service queue
safely, since the throughput of each active queue is guaranteed to
be equivalent.

Test procedure:
run "fio -numjobs=1 -ioengine=psync -bs=4k -direct=1 -rw=randread..." in
different cgroup(not root).

Test result: total bandwidth(Mib/s)
| total jobs | before this patch | after this patch      |
| ---------- | ----------------- | --------------------- |
| 1          | 33.8              | 33.8                  |
| 2          | 33.8              | 65.4 (32.7 each job)  |
| 4          | 33.8              | 106.8 (26.7 each job) |
| 8          | 33.8              | 126.4 (15.8 each job) |

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 block/bfq-iosched.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index e5a1093ec30a..b78fe8a1537e 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -268,6 +268,15 @@ static struct kmem_cache *bfq_pool;
  */
 #define BFQ_RATE_SHIFT		16
 
+/*
+ * 1) bfq keep dispatching requests with same size for at least one second.
+ * 2) bfq dispatch at lease 1024 requests
+ *
+ * We think bfq are dispatching request with same size if the above two
+ * conditions hold true.
+ */
+#define VARIED_REQUEST_SIZE(bfqd) ((bfqd)->dispatch_count < 1024 ||\
+		time_before(jiffies, (bfqd)->dispatch_time + HZ))
 /*
  * When configured for computing the duration of the weight-raising
  * for interactive queues automatically (see the comments at the
@@ -724,7 +733,8 @@ static bool bfq_asymmetric_scenario(struct bfq_data *bfqd,
 	bool multiple_classes_busy;
 
 #ifdef CONFIG_BFQ_GROUP_IOSCHED
-	if (bfqd->num_groups_with_pending_reqs > 1)
+	if (bfqd->num_groups_with_pending_reqs > 1 &&
+	    VARIED_REQUEST_SIZE(bfqd))
 		return true;
 #endif
 
-- 
2.31.1


  parent reply	other threads:[~2021-07-14  9:37 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-14  9:45 [PATCH 0/3] optimize the queue idle judgment Yu Kuai
2021-07-14  9:45 ` [PATCH 1/3] block, bfq: do not idle if only one cgroup is activated Yu Kuai
2021-07-24  7:12   ` Paolo Valente
2021-07-26  1:15     ` yukuai (C)
2021-07-31  7:10     ` yukuai (C)
2021-08-03  7:07       ` Paolo Valente
2021-08-03 11:30         ` yukuai (C)
2021-07-14  9:45 ` [PATCH 2/3] block, bfq: add support to record request size information Yu Kuai
2021-07-14  9:45 ` Yu Kuai [this message]
2021-07-20 12:33 ` [PATCH 0/3] optimize the queue idle judgment yukuai (C)

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