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[90.86.61.78]) by smtp.gmail.com with ESMTPSA id q24sm971429wmc.43.2019.06.07.00.30.11 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 07 Jun 2019 00:30:11 -0700 (PDT) Subject: Re: [PATCH 0/2] block, bfq: add weight symlink to the bfq.weight cgroup parameter To: Paolo Valente Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, ulf.hansson@linaro.org, linus.walleij@linaro.org, broonie@kernel.org, bfq-iosched@googlegroups.com, oleksandr@natalenko.name References: <20190521080155.36178-1-paolo.valente@linaro.org> From: Jens Axboe Message-ID: <854dd83a-bd07-c1c3-d005-ef7a62f0fa35@kernel.dk> Date: Fri, 7 Jun 2019 01:30:10 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190521080155.36178-1-paolo.valente@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/21/19 2:01 AM, Paolo Valente wrote: > 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. Applied, thanks. -- Jens Axboe