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docs/cgroup-v1/blkio: update for 5.x kernels 

Commit bf382fb0bcef4 ("block: remove legacy IO schedulers", Oct 12 2018)
removes the CFQ scheduler, together with blkio.weight and
blkio.weight_device described in cgroup v1 documentation. Users are
supposed to use the BFQ scheduler, which cgroup file for setting weight
is blkio.bfq.weight, but there is no way to set per-device weight.

Later, commit 795fe54c2a per-device weights for BFQ, meaning that
blkio.bfq.weight and blkio.bfq.weight_device can be used in a way
similar to the old CFQ cgroup interface.

Yet, the cgroup v1 docs were never updated. Fix this:
 - use the new file names;
 - fix the range for weight (used to be 10..1000, now 1..1000);
 - link to BFQ scheduler docs.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Kir Kolyshkin 2021-06-10 20:07:37 -07:00 committed by Jens Axboe
parent 37fe403898
commit 828615950b
1 changed files with 16 additions and 15 deletions
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31
Documentation/admin-guide/cgroup-v1/blkio-controller.rst
View File

@ -97,40 +97,41 @@ Details of cgroup files
Proportional weight policy files
--------------------------------
blkio.weight
blkio.bfq.weight
Specifies per cgroup weight. This is default weight of the group
on all the devices until and unless overridden by per device rule.
(See blkio.weight_device).
Currently allowed range of weights is from 10 to 1000.
on all the devices until and unless overridden by per device rule
(see `blkio.bfq.weight_device` below).
blkio.weight_device
One can specify per cgroup per device rules using this interface.
These rules override the default value of group weight as specified
by blkio.weight.
Currently allowed range of weights is from 1 to 1000. For more details,
see Documentation/block/bfq-iosched.rst.
blkio.bfq.weight_device
Specifes per cgroup per device weights, overriding the default group
weight. For more details, see Documentation/block/bfq-iosched.rst.
Following is the format::
# echo dev_maj:dev_minor weight > blkio.weight_device
# echo dev_maj:dev_minor weight > blkio.bfq.weight_device
Configure weight=300 on /dev/sdb (8:16) in this cgroup::
# echo 8:16 300 > blkio.weight_device
# cat blkio.weight_device
# echo 8:16 300 > blkio.bfq.weight_device
# cat blkio.bfq.weight_device
dev weight
8:16 300
Configure weight=500 on /dev/sda (8:0) in this cgroup::
# echo 8:0 500 > blkio.weight_device
# cat blkio.weight_device
# echo 8:0 500 > blkio.bfq.weight_device
# cat blkio.bfq.weight_device
dev weight
8:0 500
8:16 300
Remove specific weight for /dev/sda in this cgroup::
# echo 8:0 0 > blkio.weight_device
# cat blkio.weight_device
# echo 8:0 0 > blkio.bfq.weight_device
# cat blkio.bfq.weight_device
dev weight
8:16 300