From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Sender: Tejun Heo Date: Fri, 22 Apr 2016 14:41:10 -0400 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: <20160422184110.GX7822@mtj.duckdns.org> References: <1454364778-25179-1-git-send-email-paolo.valente@linaro.org> <1454364778-25179-11-git-send-email-paolo.valente@linaro.org> <20160211222824.GD3741@mtj.duckdns.org> <57174CA7.5000706@linaro.org> <20160422181321.GV7822@mtj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: List-ID: Hello, Paolo. On Fri, Apr 22, 2016 at 08:19:47PM +0200, Paolo Valente wrote: > > So, a kworker would jump through different workqueues and issue IOs > > for different writeback domains and the context can't be tied to the > > issuing task. The cgroup membership should be determined directly > > from the bio. > > Yes. My doubt arises from the fact that the only source of intense I/O > is the dd (I have executed it alone). In contrast, group changes occur > at a high frequency during all the execution of the dd. Apparently I > cannot see any other I/O induced by the dd. Journaling issues sync > requests. > > > cfq uses per-cgroup async queue. I'm not sure how this > > would map to bfq tho. > > It’s the same. But this is the part I’m checking. Ah, right, I was confused. cic is always associated with the task and yes a writeback worker can trigger blkcg changed events frequently as it walks through different cgroups. Is this an issue? Thanks. -- tejun