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From: Tejun Heo <tj@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jens Axboe <axboe@kernel.dk>,
	Paolo Valente <paolo.valente@linaro.org>,
	Li Zefan <lizefan@huawei.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Johannes Thumshirn <jthumshirn@suse.de>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Fam Zheng <fam@euphon.net>
Subject: Re: [PATCH block/for-5.2-fixes] bfq: use io.weight interface file instead of io.bfq.weight
Date: Tue, 11 Jun 2019 14:17:18 -0700
Message-ID: <20190611211718.GM3341036@devbig004.ftw2.facebook.com> (raw)
In-Reply-To: <20190611194959.GJ3341036@devbig004.ftw2.facebook.com>

On Tue, Jun 11, 2019 at 12:49:59PM -0700, Tejun Heo wrote:
> (Description mostly stolen from 19e9da9e86c4 ("block, bfq: add weight
> symlink to the bfq.weight cgroup parameter")
> 
> 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).

Sorry, please don't apply this patch.  The cgroup interface currently
implemented by bfq doesn't follow the io.weight interface spec.  It's
different from cfq interface and symlinking to or renaming it won't do
anybody any good.

For now, the only thing we can do looks like keeping it as-is.

Thanks.

-- 
tejun

  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-08  8:20 [GIT PULL] Block fixes for 5.2-rc4 Jens Axboe
2019-06-08 19:28 ` Linus Torvalds
2019-06-09  5:59   ` Jens Axboe
2019-06-09 16:06     ` Linus Torvalds
2019-06-10 10:15       ` Jens Axboe
2019-06-10 14:49         ` Paolo Valente
2019-06-10 15:48           ` Tejun Heo
2019-06-11 19:49             ` [PATCH block/for-5.2-fixes] bfq: use io.weight interface file instead of io.bfq.weight Tejun Heo
2019-06-11 21:17               ` Tejun Heo [this message]
2019-06-12  7:32                 ` Paolo Valente
2019-06-12 13:39                   ` Tejun Heo
2019-06-13  6:10                     ` Paolo Valente
2019-06-14 20:22                       ` Tejun Heo
2019-06-14 21:05                         ` Paolo Valente
2019-06-08 19:30 ` [GIT PULL] Block fixes for 5.2-rc4 pr-tracker-bot

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