Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S968056Ab2ERVj0 (ORCPT ); Fri, 18 May 2012 17:39:26 -0400 Received: from mail-qc0-f174.google.com ([209.85.216.174]:37464 "EHLO mail-qc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S968013Ab2ERVjY convert rfc822-to-8bit (ORCPT ); Fri, 18 May 2012 17:39:24 -0400 MIME-Version: 1.0 In-Reply-To: <1337375946.7562.11.camel@gandalf.stny.rr.com> References: <1337365643-29261-1-git-send-email-snanda@chromium.org> <20120518183756.GA3216@kroah.com> <1337368492.7562.8.camel@gandalf.stny.rr.com> <1337375946.7562.11.camel@gandalf.stny.rr.com> From: Sameer Nanda Date: Fri, 18 May 2012 14:39:02 -0700 X-Google-Sender-Auth: ZwZRymQ0SsL6jEs9wNhxgs1Awfg Message-ID: Subject: Re: [PATCH] power, trace: add tracing for device_resume To: Steven Rostedt Cc: Greg KH , rob@landley.net, len.brown@intel.com, pavel@ucw.cz, rjw@sisk.pl, fweisbec@gmail.com, mingo@redhat.com, jkosina@suse.cz, standby24x7@gmail.com, jj@chaosbits.net, paulmck@linux.vnet.ibm.com, josh@joshtriplett.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2275 Lines: 56 On Fri, May 18, 2012 at 2:19 PM, Steven Rostedt wrote: > On Fri, 2012-05-18 at 13:58 -0700, Sameer Nanda wrote: >> On Fri, May 18, 2012 at 12:14 PM, Steven Rostedt wrote: >> > On Fri, 2012-05-18 at 11:57 -0700, Sameer Nanda wrote: >> > >> >> AFAICT, they are used for something completely different -- help solve >> >> suspend/resume issues by saving a hash in the RTC of the last device >> >> that suspended/resumed.  They don't use the perf tracing mechanism at >> >> all. >> >> >> > >> > Also note that all tracepoints have timestamps attached to them. You do >> > not need to add deltas. Do that in the userspace tools that read the >> > timestamps and events. This way you can have one DECLARE_EVENT_CLASS and >> > three DEFINE_EVENTs. This will save space. >> >> Agreed on the space savings.  However, with the time_delta in the >> trace message itself, a one line shell script [1] that sorts on the >> time_delta field is sufficient to quickly spot the devices that take a >> long time to resume.  Without the time_delta field, the user tool is >> more complex since it needs to first match up the device_resume_in, >> device_resume_waited and device_resume_out traces and then calculate >> time deltas. >> >> Seems like a worthwhile trade-off to me but I can take out the >> time_delta if the general consensus is otherwise. > > Just note that every TRACE_EVENT() adds around 5k or more code. Every > DEFINE_EVENT adds just about 300 bytes. Ok, let me respin the patch. I am thinking of adding time_delta to all three traces. That way we should get the space saving while still allowing quick spotting of devices that take long time to resume. > >> [1]: here's an example script I use for sorting the device resume times: >> cat /sys/kernel/debug/tracing/trace | grep device_resume_out | awk >> 'BEGIN { FS = "time_delta=" } ; { print $2 $0 }' | sort -n >> > > Question is, how often is this done? And that 5k is permanent for all > users. > > -- Steve > > -- Sameer -- 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/