From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752638AbbIPQPy (ORCPT ); Wed, 16 Sep 2015 12:15:54 -0400 Received: from foss.arm.com ([217.140.101.70]:37371 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751838AbbIPQPw (ORCPT ); Wed, 16 Sep 2015 12:15:52 -0400 Date: Wed, 16 Sep 2015 17:16:05 +0100 From: Lorenzo Pieralisi To: Jisheng Zhang Cc: Catalin Marinas , Will Deacon , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH] arm64: add cpu_idle tracepoints to arch_cpu_idle Message-ID: <20150916161605.GA29663@red-moon> References: <1442413401-2955-1-git-send-email-jszhang@marvell.com> <20150916144738.GA23245@red-moon> <20150916225312.0d4d32c5@xhacker> <20150916231105.11a0e65e@xhacker> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150916231105.11a0e65e@xhacker> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 16, 2015 at 04:11:05PM +0100, Jisheng Zhang wrote: > Dear Lorenzo, > > On Wed, 16 Sep 2015 22:53:12 +0800 > Jisheng Zhang wrote: > > > Dear Lorenzo, > > > > On Wed, 16 Sep 2015 15:47:38 +0100 > > Lorenzo Pieralisi wrote: > > > > > On Wed, Sep 16, 2015 at 03:23:21PM +0100, Jisheng Zhang wrote: > > > > Currently, if cpuidle is disabled or not supported, powertop reports > > > > zero wakeups and zero events. This is due to the cpu_idle tracepoints > > > > are missing. > > > > > > > > This patch is to make cpu_idle tracepoints always available even if > > > > cpuidle is disabled or not supported. > > > > > > > > Signed-off-by: Jisheng Zhang > > > > > > Is there a reason why this code cannot be moved to the generic idle loop ? > > > > Do you mean the cpu_idle_loop() in kernel/sched/idle.c? To be honest, I > > Maybe I know now. we need to trace different idle level, for example: > > WFI idle: trace_cpu_idle_rcuidle(1, ...); > > deeper idle: trace_cpu_idle_rcuidle(2, ...); > > Usually, the first argument of trace_cpu_idle_rcuidle() equals to the index > of the idle level. > > so generic idle loop is not a good candidate. You are adding a trace for tracing state 1 (ie default idle state), called from arch_cpu_idle(), which is the default idle call when the CPUidle framework is not available, so I suggested moving the traces you add to arm/arm64 arch_cpu_idle() calls to kernel/sched/idle.c (see default_idle_call()) instead of patching architecture code. I think you can't do that because on x86 calling arch_cpu_idle() does not always mean entering idle state index 1 if I read the code correctly (in particular the mwait based implementation - mwait_idle()). So never mind, patch is fine (on arm64, on arm you should be careful because some arm_pm_idle implementations trace state 1 already - see omap3_pm_idle and if you add traces to arch_cpu_idle you should remove the traces from mach implementations). Acked-by: Lorenzo Pieralisi