From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lina Iyer Subject: Re: [PATCH v2 2/4] QoS: Enhance framework to support per-cpu PM QoS request Date: Wed, 27 Aug 2014 14:13:00 -0600 Message-ID: <20140827201300.GA79706@ilina-mac.domain> References: <1407945689-18494-1-git-send-email-lina.iyer@linaro.org> <1407945689-18494-3-git-send-email-lina.iyer@linaro.org> <7hd2blerqz.fsf@paris.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Return-path: Received: from mail-pa0-f50.google.com ([209.85.220.50]:43581 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964818AbaH0UNQ (ORCPT ); Wed, 27 Aug 2014 16:13:16 -0400 Received: by mail-pa0-f50.google.com with SMTP id et14so1152543pad.23 for ; Wed, 27 Aug 2014 13:13:12 -0700 (PDT) Content-Disposition: inline In-Reply-To: <7hd2blerqz.fsf@paris.lan> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Kevin Hilman Cc: daniel.lezcano@linaro.org, ulf.hansson@linaro.org, linux-pm@vger.kernel.org, tglx@linutronix.de, rjw@rjwysocki.net, Praveen Chidambaram On Wed, Aug 27, 2014 at 11:01:40AM -0700, Kevin Hilman wrote: >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'm curious if you looked at using the per-device QoS API for this >instead of expending the system-wide API. IOW, from a per-device QoS >POV, a CPU is no different than any other device, and since we already >have the per-device QoS API, I wondered if that might be a better choice >to implment this per-CPU feature. > If you mean dev-pm-qos, then yes. I explored using that. The dev-pm-qos is an user of the qos framework and holds an pm-qos object, but not in any other way influences the final value of the QoS constraint other than specify a request on behalf of the device. IMHO, What we want is complementary. When a device specifies a request, we want the request to be directed at a set of cpus and that is a function of the QoS framework, hence addressed by these patches to the QoS framework. >Kevin >-- >To unsubscribe from this list: send the line "unsubscribe linux-pm" in >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html