From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.7 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id A0C0F7D2F0 for ; Fri, 26 Jul 2019 20:41:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726305AbfGZUlM (ORCPT ); Fri, 26 Jul 2019 16:41:12 -0400 Received: from ms.lwn.net ([45.79.88.28]:52136 "EHLO ms.lwn.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726184AbfGZUlM (ORCPT ); Fri, 26 Jul 2019 16:41:12 -0400 Received: from lwn.net (localhost [127.0.0.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ms.lwn.net (Postfix) with ESMTPSA id 885E44BF; Fri, 26 Jul 2019 20:41:11 +0000 (UTC) Date: Fri, 26 Jul 2019 14:41:10 -0600 From: Jonathan Corbet To: Phil Frost Cc: Ingo Molnar , trivial@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Correct documentation for /proc/schedstat Message-ID: <20190726144110.3b12ae56@lwn.net> In-Reply-To: <20190724185029.26822-1-indigo@bitglue.com> References: <20190724185029.26822-1-indigo@bitglue.com> Organization: LWN.net MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Wed, 24 Jul 2019 11:50:27 -0700 Phil Frost wrote: > Commit 425e0968a25fa3f111f9919964cac079738140b5 ("sched: move code into > kernel/sched_stats.h") appears to have inadvertently changed the unit of > time from jiffies to nanoseconds as part of the implementation of CFS. > > Signed-off-by: Phil Frost > --- > Documentation/scheduler/sched-stats.txt | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/Documentation/scheduler/sched-stats.txt b/Documentation/scheduler/sched-stats.txt > index 8259b34a66ae..b6c1807a01b3 100644 > --- a/Documentation/scheduler/sched-stats.txt > +++ b/Documentation/scheduler/sched-stats.txt > @@ -19,6 +19,11 @@ are no architectures which need more than three domain levels. The first > field in the domain stats is a bit map indicating which cpus are affected > by that domain. > > +2.6.23 introduced the CFS scheduler, and also an inadvertent > +backwards-incompatible change to the statistics. Although the schedstat version > +is 14 in either case, in 2.6.23 and later, counters accumulate time in > +nanoseconds. Prior to that, jiffies. Clearly, making the documentation correct is a good thing to do. I do have to wonder if we really have to document how things were 12 years ago as well, though. Anybody who is unfortunate enough to be dealing with a pre-2.6.23 kernel will want to refer to the documentation files shipped with that kernel rather than what we have now. So I'd recommend just making the file reflect the current state of affairs. Thanks, jon