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SubjectRe: [PATCH 0/2] block, bfq: add weight symlink to the bfq.weight cgroup parameter
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> Il giorno 30 mag 2019, alle ore 17:02, Paolo Valente <paolo.valente@linaro.org> ha scritto:
>
> Hi Jens,
> have you had time to look into this?
>
> Thanks,
> Paolo
>
>> Il giorno 21 mag 2019, alle ore 10:01, Paolo Valente <paolo.valente@linaro.org> ha scritto:
>>
>> Many userspace tools and services use the proportional-share policy of
>> the blkio/io cgroups controller. The CFQ I/O scheduler implemented
>> this policy for the legacy block layer. To modify the weight of a
>> group in case CFQ was in charge, the 'weight' parameter of the group
>> must be modified. On the other hand, the BFQ I/O scheduler implements
>> the same policy in blk-mq, but, with BFQ, the parameter to modify has
>> a different name: bfq.weight (forced choice until legacy block was
>> present, because two different policies cannot share a common parameter
>> in cgroups).
>>
>> Due to CFQ legacy, most if not all userspace configurations still use
>> the parameter 'weight', and for the moment do not seem likely to be
>> changed. But, when CFQ went away with legacy block, such a parameter
>> ceased to exist.
>>
>> So, a simple workaround has been proposed by Johannes [1] to make all
>> configurations work: add a symlink, named weight, to bfq.weight. This
>> pair of patches adds:
>> 1) the possibility to create a symlink to a cgroup file;
>> 2) the above 'weight' symlink.
>>
>> Thanks,
>> Paolo
>>
>> [1] https://lkml.org/lkml/2019/4/8/555
>>
>> Angelo Ruocco (2):
>> cgroup: let a symlink too be created with a cftype file
>> block, bfq: add weight symlink to the bfq.weight cgroup parameter
>>
>> block/bfq-cgroup.c | 6 ++++--
>> include/linux/cgroup-defs.h | 3 +++
>> kernel/cgroup/cgroup.c | 33 +++++++++++++++++++++++++++++----
>> 3 files changed, 36 insertions(+), 6 deletions(-)
>>
>> --
>> 2.20.1
>

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