Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756699Ab0FCPsj (ORCPT ); Thu, 3 Jun 2010 11:48:39 -0400 Received: from mga11.intel.com ([192.55.52.93]:61845 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755224Ab0FCPsi convert rfc822-to-8bit (ORCPT ); Thu, 3 Jun 2010 11:48:38 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.53,355,1272870000"; d="scan'208";a="573020918" From: "Gross, Mark" To: Kevin Hilman , Peter Zijlstra CC: Alan Cox , Florian Mickler , James Bottomley , =?iso-8859-1?Q?Arve_Hj=F8nnev=E5g?= , Neil Brown , "tytso@mit.edu" , LKML , Thomas Gleixner , Linux OMAP Mailing List , Linux PM , "felipe.balbi@nokia.com" Date: Thu, 3 Jun 2010 07:52:38 -0700 Subject: RE: [linux-pm] [PATCH 0/8] Suspend block api (version 8) Thread-Topic: [linux-pm] [PATCH 0/8] Suspend block api (version 8) Thread-Index: AcsDKwjaBiK236F5T0+hG6jMXwbpuAAAKr1g Message-ID: References: <20100527232357.6d14fdb2@lxorguk.ukuu.org.uk> <20100601135102.GA8098@srcf.ucam.org> <1275426085.21962.967.camel@mulgrave.site> <201006020024.14220.rjw@sisk.pl> <1275431816.21962.1108.camel@mulgrave.site> <1275451342.21962.1777.camel@mulgrave.site> <1275491111.2799.110.camel@mulgrave.site> <20100602214748.7742e3ae@schatten.dmk.lab> <1275511271.2799.516.camel@mulgrave.site> <20100603010607.5baf82a6@schatten.dmk.lab> <20100603110312.48a508dc@lxorguk.ukuu.org.uk> <1275559512.27810.35287.camel@twins> <87d3w818ki.fsf@deeprootsystems.com> In-Reply-To: <87d3w818ki.fsf@deeprootsystems.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2243 Lines: 53 >-----Original Message----- >From: Kevin Hilman [mailto:khilman@deeprootsystems.com] >Sent: Thursday, June 03, 2010 7:43 AM >To: Peter Zijlstra >Cc: Alan Cox; Gross, Mark; Florian Mickler; James Bottomley; Arve >Hj?nnev?g; Neil Brown; tytso@mit.edu; LKML; Thomas Gleixner; Linux OMAP >Mailing List; Linux PM; felipe.balbi@nokia.com >Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8) > >Peter Zijlstra writes: > >> On Thu, 2010-06-03 at 11:03 +0100, Alan Cox wrote: >>> > [mtg: ] This has been a pain point for the PM_QOS implementation. >>> They change the constrain back and forth at the transaction level of >>> the i2c driver. The pm_qos code really wasn't made to deal with such >>> hot path use, as each such change triggers a re-computation of what >>> the aggregate qos request is. >>> >>> That should be trivial in the usual case because 99% of the time you can >>> hot path >>> >>> the QoS entry changing is the latest one >>> there have been no other changes >>> If it is valid I can use the cached previous aggregate I cunningly >>> saved in the top QoS entry when I computed the new one >>> >>> (ie most of the time from the kernel side you have a QoS stack) >> >> Why would the kernel change the QoS state of a task? Why not have two >> interacting QoS variables, one for the task, one for the subsystem in >> question, and the action depends on their relative value? > >Yes, having a QoS parameter per-subsystem (or even per-device) is very >important for SoCs that have independently controlled powerdomains. >If all devices/subsystems in a particular powerdomain have QoS >parameters that permit, the power state of that powerdomain can be >lowered independently from system-wide power state and power states of >other power domains. > This seems similar to that pm_qos generalization into bus drivers we where waving our hands at during the collab summit in April? We never did get into meaningful detail at that time. --mgross -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/