From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5395FC43219 for ; Fri, 3 May 2019 14:56:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2E0A32070B for ; Fri, 3 May 2019 14:56:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728169AbfECO42 (ORCPT ); Fri, 3 May 2019 10:56:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:36250 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726992AbfECO42 (ORCPT ); Fri, 3 May 2019 10:56:28 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A040D2070B; Fri, 3 May 2019 14:56:27 +0000 (UTC) Date: Fri, 3 May 2019 10:56:26 -0400 From: Steven Rostedt To: Tzvetomir Stoyanov Cc: linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org, tom.zanussi@linux.intel.com Subject: Re: [PATCH] Documentation/trace: Add clarification how histogram onmatch works Message-ID: <20190503105626.453d32c4@gandalf.local.home> In-Reply-To: <20190503143537.19752-1-tstoyanov@vmware.com> References: <20190503143537.19752-1-tstoyanov@vmware.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 3 May 2019 17:35:37 +0300 Tzvetomir Stoyanov wrote: > The current trace documentation, the section describing histogram's "onmatch" > is not straightforward enough about how this action is applied. It is not > clear what criteria are used to "match" both events. A short note is added, > describing what exactly is compared in order to match the events. Hi Tzvetomir, Thanks for sending this. Some minor tweaks below. > > Signed-off-by: Tzvetomir Stoyanov > --- > Documentation/trace/histogram.txt | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/Documentation/trace/histogram.txt b/Documentation/trace/histogram.txt > index 7ffea6aa22e3..b75a75cfab8c 100644 > --- a/Documentation/trace/histogram.txt > +++ b/Documentation/trace/histogram.txt > @@ -1863,7 +1863,10 @@ hist trigger specification. > > The 'matching.event' specification is simply the fully qualified > event name of the event that matches the target event for the > - onmatch() functionality, in the form 'system.event_name'. > + onmatch() functionality, in the form 'system.event_name'. Histogram > + keys of both events are compared to find if events match. In case > + multiple histogram keys are used, they all must match in the specified > + order. I would reword that to be: In the case that multiple histogram keys are used, both events must have the same number of keys, and the keys must match in the same order. > > Finally, the number and type of variables/fields in the 'param > list' must match the number and types of the fields in the > @@ -1920,9 +1923,9 @@ hist trigger specification. > /sys/kernel/debug/tracing/events/sched/sched_waking/trigger > > Then, when the corresponding thread is actually scheduled onto the > - CPU by a sched_switch event, calculate the latency and use that > - along with another variable and an event field to generate a > - wakeup_latency synthetic event: > + CPU by a sched_switch event (saved_pid matches next_pid), calculate CPU by a sched_switch event (where the sched_waking key "saved_pid" matches the sched_switch key "next_pid"), Other than that, looks good. Could you send a v2 with the updates? Thanks! -- Steve > + the latency and use that along with another variable and an event field > + to generate a wakeup_latency synthetic event: > > # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:\ > onmatch(sched.sched_waking).wakeup_latency($wakeup_lat,\