From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Sender: Tejun Heo Date: Thu, 11 Feb 2016 17:28:24 -0500 From: Tejun Heo To: Paolo Valente Cc: Jens Axboe , Fabio Checconi , Arianna Avanzini , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, ulf.hansson@linaro.org, linus.walleij@linaro.org, broonie@kernel.org Subject: Re: [PATCH RFC 10/22] block, bfq: add full hierarchical scheduling and cgroups support Message-ID: <20160211222824.GD3741@mtj.duckdns.org> References: <1454364778-25179-1-git-send-email-paolo.valente@linaro.org> <1454364778-25179-11-git-send-email-paolo.valente@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1454364778-25179-11-git-send-email-paolo.valente@linaro.org> List-ID: Hello, On Mon, Feb 01, 2016 at 11:12:46PM +0100, Paolo Valente wrote: > From: Arianna Avanzini > > Complete support for full hierarchical scheduling, with a cgroups > interface. The name of the added policy is bfq. > > Weights can be assigned explicitly to groups and processes through the > cgroups interface, differently from what happens, for single > processes, if the cgroups interface is not used (as explained in the > description of the previous patch). In particular, since each node has > a full scheduler, each group can be assigned its own weight. * It'd be great if how cgroup support is achieved is better documented. * How's writeback handled? * After all patches are applied, both CONFIG_BFQ_GROUP_IOSCHED and CONFIG_CFQ_GROUP_IOSCHED exist. * The default weight and weight range don't seem to follow the defined interface on the v2 hierarchy. The default value should be 100. * With all patches applied, booting triggers a RCU context warning. Please build with lockdep and RCU debugging turned on and fix the issue. * I was testing on the v2 hierarchy with two top-level cgroups one hosting sequential workload and the other completely random. While they eventually converged to a reasonable state, starting up the sequential workload while the random workload was running was extremely slow. It crawled for quite a while. * And "echo 100 > io.weight" hung the writing process. Thanks. -- tejun