From mboxrd@z Thu Jan 1 00:00:00 1970 From: Colin Cross Subject: Re: [RFC PATCH] power: Add option to log time spent in suspend Date: Thu, 2 May 2013 12:11:50 -0700 Message-ID: References: <1367360914-23389-1-git-send-email-zoran.markovic@linaro.org> <1367360914-23389-2-git-send-email-zoran.markovic@linaro.org> <20130501002929.GA20042@amd.pavel.ucw.cz> <20130502122747.GA22618@amd.pavel.ucw.cz> <5182B74E.8060909@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Return-path: Received: from mail-ve0-f173.google.com ([209.85.128.173]:36948 "EHLO mail-ve0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761871Ab3EBTLv (ORCPT ); Thu, 2 May 2013 15:11:51 -0400 Received: by mail-ve0-f173.google.com with SMTP id ox1so855455veb.4 for ; Thu, 02 May 2013 12:11:50 -0700 (PDT) In-Reply-To: <5182B74E.8060909@linaro.org> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: John Stultz Cc: Pavel Machek , Zoran Markovic , lkml , Linux PM list , Android Kernel Team , Todd Poynor , San Mehat , Benoit Goby , "Rafael J. Wysocki" , Len Brown On Thu, May 2, 2013 at 11:58 AM, John Stultz wrote: > On 05/02/2013 11:29 AM, Colin Cross wrote: >> >> On Thu, May 2, 2013 at 5:27 AM, Pavel Machek wrote: >>> >>> >>>> dmesg is not the solution, it's not a stable api, it would require >>>> constant parsing to make sure you didn't miss data before it fell out >>>> of the ringbuffer, and sched_clock often does not (and should not) >>>> tick during suspend, so printk times don't show the time spent >>>> suspended. >>> >>> If timing info printed is invalid, that should be fixed. >> >> It's not invalid, its just not measuring the time that is useful here. >> printk is measuring something similar to (but not exactly the same >> as) CLOCK_MONOTONIC, but this is measuring something similar to >> CLOCK_BOOTTIME. > > > One thing I'm curious about with this patch, since we measure and keep track > of suspend time in the timekeeping core, there may be enough justification > to adding this sort of debugging info the timekeeping core itself. > > Although what is being tracked with this driver isn't just total time in > suspend, but looks like more of a logarithmic histogram of suspend times. Is > there any context you can provide as to why that particular format was > chosen (which would could be added to help improve the commit message)? The idea was to keep a minimal amount of data while still being able to see how often the device is waking up.