From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hilman Subject: Re: [PATCH v2 2/4] QoS: Enhance framework to support per-cpu PM QoS request Date: Mon, 18 Aug 2014 16:55:41 -0700 Message-ID: <7h4mx9wdxe.fsf@paris.lan> References: <1407945689-18494-1-git-send-email-lina.iyer@linaro.org> <1407945689-18494-3-git-send-email-lina.iyer@linaro.org> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from mail-pd0-f179.google.com ([209.85.192.179]:56935 "EHLO mail-pd0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751245AbaHRXzo (ORCPT ); Mon, 18 Aug 2014 19:55:44 -0400 Received: by mail-pd0-f179.google.com with SMTP id v10so8405123pde.10 for ; Mon, 18 Aug 2014 16:55:43 -0700 (PDT) In-Reply-To: <1407945689-18494-3-git-send-email-lina.iyer@linaro.org> (Lina Iyer's message of "Wed, 13 Aug 2014 10:01:27 -0600") Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Lina Iyer Cc: daniel.lezcano@linaro.org, ulf.hansson@linaro.org, linux-pm@vger.kernel.org, tglx@linutronix.de, rjw@rjwysocki.net, Praveen Chidambaram Hi Lina, Lina Iyer writes: > QoS request can be better optimized if the request can be set only for > the required cpus and not all cpus. This helps save power on other > cores, while still gauranteeing the quality of service on the desired > cores. > > Add a new enumeration to specify the PM QoS request type. The enums help > specify what is the intended target cpu of the request. > > Enhance the QoS constraints data structures to support target value for > each core. Requests specify if the QoS is applicable to all cores > (default) or to a selective subset of the cores or to a core(s). > > Idle and interested drivers can request a PM QoS value for a constraint > across all cpus, or a specific cpu or a set of cpus. Separate APIs have > been added to request for individual cpu or a cpumask. The default > behaviour of PM QoS is maintained i.e, requests that do not specify a > type of the request will continue to be effected on all cores. > > The userspace sysfs interface does not support setting cpumask of a PM > QoS request. > > Signed-off-by: Praveen Chidambaram > Signed-off-by: Lina Iyer I agree this is a needed feature. I didn't study it in detail yet, but after a quick glance, it looks like a good approach. However, I did start to wonder how this will behave in the context of the hotplug. For example, what if a constraint is setup with a cpumask, then one of those CPUs is hotplugged away. Kevin