From: brookxu <brookxu.cn@gmail.com>
To: paolo.valente@linaro.org, axboe@kernel.dk, tj@kernel.org
Cc: linux-block@vger.kernel.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [RFC PATCH 2/8] bfq: limit the IO depth of idle_class to 1
Date: Mon, 8 Mar 2021 20:00:15 +0800 [thread overview]
Message-ID: <c23ff2bafdf20b3f18debfa1021e59a87aba1a11.1615203034.git.brookxu@tencent.com> (raw)
In-Reply-To: <cover.1615203034.git.brookxu@tencent.com>
In-Reply-To: <cover.1615203034.git.brookxu@tencent.com>
From: Chunguang Xu <brookxu@tencent.com>
From: Chunguang Xu <brookxu@tencent.com>
The IO depth of idle_class 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 ec482e6641ff..ea9d7f6f4e3d 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 idle_class 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) {
--
2.30.0
next prev parent reply other threads:[~2021-03-08 12:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-08 12:00 [RFC PATCH 0/8] bfq: introduce bfq.ioprio for cgroup brookxu
2021-03-08 12:00 ` [RFC PATCH 1/8] bfq: introduce bfq_entity_to_bfqg helper method brookxu
2021-03-08 12:00 ` brookxu [this message]
2021-03-08 12:00 ` [RFC PATCH 3/8] bfq: keep the minimun bandwidth for be_class brookxu
2021-03-08 12:00 ` [RFC PATCH 4/8] bfq: expire bfqq if a higher priority class is waiting brookxu
2021-03-08 12:00 ` [RFC PATCH 5/8] bfq: introduce bfq.ioprio for cgroup brookxu
2021-03-08 12:00 ` [RFC PATCH 6/8] bfq: convert the type of bfq_group.bfqd to bfq_data* brookxu
2021-03-08 12:00 ` [RFC PATCH 7/8] bfq: remove unnecessary initialization logic brookxu
2021-03-08 12:00 ` [RFC PATCH 8/8] bfq: optimize the calculation of bfq_weight_to_ioprio() brookxu
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