From: brookxu <brookxu.cn@gmail.com>
To: paolo.valente@linaro.org, axboe@kernel.dk
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [RESEND PATCH 3/8] bfq: limit the IO depth of CLASS_IDLE to 1
Date: Thu, 10 Jun 2021 15:22:32 +0800 [thread overview]
Message-ID: <34edd545a9f6f6b327fc6779fbd17fd3a519ed4c.1618916839.git.brookxu@tencent.com> (raw)
Message-ID: <20210610072232.lT9oUiJ6U64HauWNK7SMhy2JbSaW-Y-GYlZoFFqf5LA@z> (raw)
In-Reply-To: <1ce935f1bb10e0c7ecea7b79b826ff4cfc89acf0.1618916839.git.brookxu@tencent.com>
In-Reply-To: <cover.1618916839.git.brookxu@tencent.com>
From: Chunguang Xu <brookxu@tencent.com>
The IO depth of queues belong to CLASS_IDLE is limited to 1,
so that it can avoid introducing a larger tail latency under
a device with a larger IO depth. Although limiting the IO
depth may reduce the performance of idle_class, it is
generally not a big problem, because idle_class usually does
not have strict performance requirements.
Signed-off-by: Chunguang Xu <brookxu@tencent.com>
---
block/bfq-iosched.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index ec482e6..29940ec 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -4808,6 +4808,17 @@ static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx)
if (!bfqq)
goto exit;
+ /*
+ * Here, the IO depth of queues belong to CLASS_IDLE is limited
+ * to 1, so that it can avoid introducing a larger tail latency
+ * under a device with a larger IO depth. Although limiting the
+ * IO depth may reduce the performance of idle_class, it is
+ * generally not a big problem, because idle_class usually
+ * does not have strict performance requirements.
+ */
+ if (bfq_class_idle(bfqq) && bfqq->dispatched)
+ goto exit;
+
rq = bfq_dispatch_rq_from_bfqq(bfqd, bfqq);
if (rq) {
--
1.8.3.1
next prev parent reply other threads:[~2021-06-10 7:23 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 11:20 [PATCH 0/8] bfq: misc updates brookxu
2021-04-20 11:20 ` [PATCH 1/8] bfq: introduce bfq_entity_to_bfqg helper method brookxu
2021-06-10 7:22 ` [RESEND PATCH " brookxu
2021-06-10 8:31 ` Oleksandr Natalenko
2021-06-10 9:05 ` brookxu
2021-06-10 9:18 ` Piotr Górski
2021-04-20 11:20 ` [PATCH 2/8] bfq: convert the type of bfq_group.bfqd to bfq_data* brookxu
2021-06-10 7:22 ` [RESEND PATCH " brookxu
2021-04-20 11:20 ` brookxu [this message]
2021-06-10 7:22 ` [RESEND PATCH 3/8] bfq: limit the IO depth of CLASS_IDLE to 1 brookxu
2021-04-20 11:20 ` [PATCH 4/8] bfq: keep the minimun bandwidth for CLASS_BE brookxu
2021-06-10 7:22 ` [RESEND PATCH " brookxu
2021-04-20 11:20 ` [PATCH 5/8] bfq: remove unnecessary initialization logic brookxu
2021-06-10 7:22 ` [RESEND PATCH " brookxu
2021-04-20 11:20 ` [PATCH 6/8] bfq: optimize the calculation of bfq_weight_to_ioprio() brookxu
2021-06-10 7:22 ` [RESEND PATCH " brookxu
2021-04-20 11:20 ` [PATCH 7/8] bfq: reset entity->prio_changed in bfq_init_entity() brookxu
2021-06-10 7:22 ` [RESEND PATCH " brookxu
2021-04-20 11:20 ` [PATCH 8/8] bfq: remove unnecessary BFQ_DEFAULT_GRP_IOPRIO brookxu
2021-06-10 7:22 ` [RESEND PATCH " brookxu
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