Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754031AbbBQFet (ORCPT ); Tue, 17 Feb 2015 00:34:49 -0500 Received: from mail-we0-f174.google.com ([74.125.82.174]:34148 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750724AbbBQFes (ORCPT ); Tue, 17 Feb 2015 00:34:48 -0500 Message-ID: <54E2D2F5.2020100@gmail.com> Date: Tue, 17 Feb 2015 06:34:45 +0100 From: "Michael Kerrisk (man-pages)" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Vince Weaver CC: mtk.manpages@gmail.com, linux-man@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo Subject: Re: [patch] perf_event_open.2: Clarify PERF_EVENT_IOC_REFRESH behavior References: In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2264 Lines: 65 On 02/12/2015 06:14 PM, Vince Weaver wrote: > > Currently the PERF_EVENT_IOC_REFRESH ioctl, when applied to a group > leader, will refresh all children. Also if a refresh value of 0 > is chosen then the refresh becomes infinite (never runs out). > Back in 2011 PAPI was relying on these behaviors but I was told > that both were unsupported and subject to being removed at any time. > (See https://lkml.org/lkml/2011/5/24/337 ) > However the behavior has not been changed. Thanks, Vince. Applied. Cheers, Michael > This patch updates the manpage to still list the behavior as > unsupported, but removes the innacurate description of it > only being a problem with 2.6 kernels. > > Signed-off-by: Vince Weaver > > diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 > index 39c8d8c..76136e2 100644 > --- a/man2/perf_event_open.2 > +++ b/man2/perf_event_open.2 > @@ -2353,6 +2353,12 @@ once the counter reaches 0 > is indicated and > the underlying event is disabled. > > +Refreshing an event group leader refreshes all siblings and > +refreshing with a parameter of 0 currently enables infinite > +refreshes; > +these behaviors are unsupported and should not be relied on. > +.\" See https://lkml.org/lkml/2011/5/24/337 > + > Starting with Linux 3.18, > .\" commit 179033b3e064d2cd3f5f9945e76b0a0f0fbf4883 > .B POLL_HUP > @@ -2805,11 +2811,6 @@ Prior to Linux 2.6.35, > .B PERF_FORMAT_GROUP > did not work with attached processes. > > -In older Linux 2.6 versions, > -refreshing an event group leader refreshed all siblings, > -and refreshing with a parameter of 0 enabled infinite refresh. > -This behavior is unsupported and should not be relied on. > - > There is a bug in the kernel code between > Linux 2.6.36 and Linux 3.0 that ignores the > "watermark" field and acts as if a wakeup_event > > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- 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/