From: Kir Kolyshkin <kolyshkin@gmail.com>
To: Jonathan Corbet <corbet@lwn.net>, linux-doc@vger.kernel.org
Cc: tj@kernel.org, axboe@kernel.dk, paolo.valente@linaro.org,
cgroups@vger.kernel.org, Kir Kolyshkin <kolyshkin@gmail.com>
Subject: [PATCH v2] docs: block/bfq: describe per-device weight
Date: Mon, 14 Jun 2021 14:41:09 -0700 [thread overview]
Message-ID: <20210614214109.207430-1-kolyshkin@gmail.com> (raw)
In-Reply-To: <8735tlbbml.fsf@meer.lwn.net>
The functionality of setting per-device weight for BFQ was added
in v5.4 (commit 795fe54c2a828099), but the documentation was never
updated.
While at it, improve formatting a bit.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
---
Documentation/block/bfq-iosched.rst | 38 ++++++++++++++++++++---------
1 file changed, 27 insertions(+), 11 deletions(-)
diff --git a/Documentation/block/bfq-iosched.rst b/Documentation/block/bfq-iosched.rst
index 66c5a4e54130..df3a8a47f58c 100644
--- a/Documentation/block/bfq-iosched.rst
+++ b/Documentation/block/bfq-iosched.rst
@@ -553,20 +553,36 @@ throughput sustainable with bfq, because updating the blkio.bfq.*
stats is rather costly, especially for some of the stats enabled by
CONFIG_BFQ_CGROUP_DEBUG.
-Parameters to set
------------------
+Parameters
+----------
-For each group, there is only the following parameter to set.
+For each group, the following parameters can be set:
-weight (namely blkio.bfq.weight or io.bfq-weight): the weight of the
-group inside its parent. Available values: 1..1000 (default 100). The
-linear mapping between ioprio and weights, described at the beginning
-of the tunable section, is still valid, but all weights higher than
-IOPRIO_BE_NR*10 are mapped to ioprio 0.
+ weight
+ This specifies the default weight for the cgroup inside its parent.
+ Available values: 1..1000 (default: 100).
-Recall that, if low-latency is set, then BFQ automatically raises the
-weight of the queues associated with interactive and soft real-time
-applications. Unset this tunable if you need/want to control weights.
+ For cgroup v1, it is set by writing the value to `blkio.bfq.weight`.
+
+ For cgroup v2, it is set by writing the value to `io.bfq.weight`.
+ (with an optional prefix of `default` and a space).
+
+ The linear mapping between ioprio and weights, described at the beginning
+ of the tunable section, is still valid, but all weights higher than
+ IOPRIO_BE_NR*10 are mapped to ioprio 0.
+
+ Recall that, if low-latency is set, then BFQ automatically raises the
+ weight of the queues associated with interactive and soft real-time
+ applications. Unset this tunable if you need/want to control weights.
+
+ weight_device
+ This specifies a per-device weight for the cgroup. The syntax is
+ `minor:major weight`. A weight of `0` may be used to reset to the default
+ weight.
+
+ For cgroup v1, it is set by writing the value to `blkio.bfq.weight_device`.
+
+ For cgroup v2, the file name is `io.bfq.weight`.
[1]
--
2.31.1
next prev parent reply other threads:[~2021-06-14 21:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-11 3:07 [PATCH 0/3] add/update/fix BFQ docs Kir Kolyshkin
2021-06-11 3:07 ` [PATCH 1/3] docs: block/bfq: describe per-device weight Kir Kolyshkin
2021-06-13 23:14 ` Jonathan Corbet
2021-06-14 21:01 ` [PATCH v2] " Kir Kolyshkin
2021-06-14 21:03 ` [PATCH 1/3] " Kirill Kolyshkin
2021-06-14 21:41 ` Kir Kolyshkin [this message]
2021-06-11 3:07 ` [PATCH 2/3] docs/cgroup-v1/blkio: stop abusing itemized list Kir Kolyshkin
2021-06-11 3:07 ` [PATCH 3/3] docs/cgroup-v1/blkio: update for 5.x kernels Kir Kolyshkin
2021-06-16 15:46 ` [PATCH 0/3] add/update/fix BFQ docs Tejun Heo
2021-06-16 17:32 ` Jens Axboe
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