Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754020AbaAaJnu (ORCPT ); Fri, 31 Jan 2014 04:43:50 -0500 Received: from e8.ny.us.ibm.com ([32.97.182.138]:43327 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751032AbaAaJnp (ORCPT ); Fri, 31 Jan 2014 04:43:45 -0500 Message-ID: <52EB6F65.8050008@linux.vnet.ibm.com> Date: Fri, 31 Jan 2014 15:09:49 +0530 From: Preeti U Murthy User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 MIME-Version: 1.0 To: Peter Zijlstra , Arjan van de Ven , Len Brown CC: Preeti Murthy , Daniel Lezcano , nicolas.pitre@linaro.org, mingo@redhat.com, Thomas Gleixner , "Rafael J. Wysocki" , LKML , "linux-pm@vger.kernel.org" , Lists linaro-kernel Subject: Re: [RFC PATCH 3/3] idle: store the idle state index in the struct rq References: <1391090962-15032-1-git-send-email-daniel.lezcano@linaro.org> <1391090962-15032-4-git-send-email-daniel.lezcano@linaro.org> <20140130153150.GD5002@laptop.programming.kicks-ass.net> <52EA7D8A.6080604@linaro.org> <20140130163501.GG5002@laptop.programming.kicks-ass.net> <52EA8B07.6020206@linaro.org> <20140131090230.GM5002@laptop.programming.kicks-ass.net> In-Reply-To: <20140131090230.GM5002@laptop.programming.kicks-ass.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14013109-0320-0000-0000-00000258FCFB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, On 01/31/2014 02:32 PM, Peter Zijlstra wrote: > On Fri, Jan 31, 2014 at 02:15:47PM +0530, Preeti Murthy wrote: >>> >>> If the driver does its own random mapping that will break the governor >>> logic. So yes, the states are ordered, the higher the index is, the more you >>> save power and the higher the exit latency is. >> >> The above point holds true for only the ladder governor which sees the idle >> states indexed in the increasing order of target_residency/exit_latency. >> >> However this is not true as far as I can see in the menu governor. It >> acknowledges the dynamic ordering of idle states as can be seen in the >> menu_select() function in the menu governor, where the idle state for the >> CPU gets chosen. You will notice that, even if it is found that the predicted >> idle time of the CPU is smaller than the target residency of an idle state, >> the governor continues to search for suitable idle states in the higher indexed >> states although it should have halted if the idle states' were ordered according >> to their target residency.. The same holds for exit_latency. >> >> Hence I think this patch would make sense only with additional information >> like exit_latency or target_residency is present for the scheduler. The idle >> state index alone will not be sufficient. > > Alternatively, can we enforce sanity on the cpuidle infrastructure to > make the index naturally ordered? If not, please explain why :-) The commit id 71abbbf856a0e70 says that there are SOCs which could have their target_residency and exit_latency values change at runtime. This commit thus removed the ordering of the idle states according to their target_residency/exit_latency. Adding Len and Arjan to the CC. Thanks Regards Preeti U Murthy > -- 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/