From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Date: Wed, 20 Jan 2016 21:22:14 +0100 (CET) Message-ID: References: <1453305636-22156-1-git-send-email-daniel.lezcano@linaro.org> <1453305636-22156-2-git-send-email-daniel.lezcano@linaro.org> <20160120190718.GS6357@twins.programming.kicks-ass.net> <20160120202014.GK6356@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: Received: from www.linutronix.de ([62.245.132.108]:33574 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753129AbcATUXS (ORCPT ); Wed, 20 Jan 2016 15:23:18 -0500 In-Reply-To: <20160120202014.GK6356@twins.programming.kicks-ass.net> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Peter Zijlstra Cc: Daniel Lezcano , rafael@kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, nicolas.pitre@linaro.org, vincent.guittot@linaro.org On Wed, 20 Jan 2016, Peter Zijlstra wrote: > On Wed, Jan 20, 2016 at 08:57:06PM +0100, Thomas Gleixner wrote: > > > Here too, ktime_get() is daft. > > > > What's the problem? ktime_xxx() itself or just the clock monotonic variant? > > > > On 99.9999% of the platforms ktime_get_mono_fast/raw_fast is not any slower > > than sched_clock(). The only case where sched_clock is faster is if your TSC > > is buggered and the box switches to HPET for timekeeping. > > The HPET thing, I just don't want to have to explain why this is so much > more expensive on some random weird machine, esp. since it really > doesn't matter. Fair enough.