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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham 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 4F23AC4360F for ; Tue, 2 Apr 2019 10:47:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2691C208E4 for ; Tue, 2 Apr 2019 10:47:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729831AbfDBKrR (ORCPT ); Tue, 2 Apr 2019 06:47:17 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:48700 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726468AbfDBKrR (ORCPT ); Tue, 2 Apr 2019 06:47:17 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AD7841688; Tue, 2 Apr 2019 03:47:16 -0700 (PDT) Received: from fuggles.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 56A583F59C; Tue, 2 Apr 2019 03:47:15 -0700 (PDT) Date: Tue, 2 Apr 2019 11:47:12 +0100 From: Will Deacon To: Alexander Shishkin Cc: Ben Gainey , "mingo@kernel.org" , "peterz@infradead.org" , "acme@redhat.com" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: BUG in "perf: Suppress AUX/OVERWRITE records"? Message-ID: <20190402104712.GD26171@fuggles.cambridge.arm.com> References: <87k1gm86en.fsf@ashishki-desk.ger.corp.intel.com> <3f04004a48a4b5bece9d277d5c51661f4eca7e97.camel@arm.com> <87wokk7k20.fsf@ashishki-desk.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87wokk7k20.fsf@ashishki-desk.ger.corp.intel.com> User-Agent: Mutt/1.11.1+86 (6f28e57d73f2) () Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 27, 2019 at 11:17:43AM +0200, Alexander Shishkin wrote: > Ben Gainey writes: > > >> It was an unintentional side effect that it also > >> happened to coincide with context switches in the overwrite mode. > > > > I'm not using overwrite mode, I'm opening the mmap with PROT_WRITE > > (i.e. in truncate mode). > > Now I get it. Does the below fix the problem for you? > > From bf52320cce0e74a2c0d987db7bd571f7687b4f4f Mon Sep 17 00:00:00 2001 > From: Alexander Shishkin > Date: Wed, 27 Mar 2019 11:05:53 +0200 > Subject: [PATCH] perf: Fix AUX record suppression > > Commit 1627314fb54a33e ("perf: Suppress AUX/OVERWRITE records") has an > unintended side-effect of also suppressing all AUX records with no flags > and non-zero size, so all the regular records in the full trace mode. > This breaks some use cases for people. > > Fix this by restoring "regular" AUX records to their former glory. > > Signed-off-by: Alexander Shishkin > Fixes: 1627314fb54a33e ("perf: Suppress AUX/OVERWRITE records") > Reported-by: Ben Gainey > CC: stable@vger.kernel.org # v4.20+ > --- > kernel/events/ring_buffer.c | 33 +++++++++++++++------------------ > 1 file changed, 15 insertions(+), 18 deletions(-) > > diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c > index 678ccec60d8f..626256dc26c1 100644 > --- a/kernel/events/ring_buffer.c > +++ b/kernel/events/ring_buffer.c > @@ -455,24 +455,21 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size) > rb->aux_head += size; > } > > - if (size || handle->aux_flags) { > - /* > - * Only send RECORD_AUX if we have something useful to communicate > - * > - * Note: the OVERWRITE records by themselves are not considered > - * useful, as they don't communicate any *new* information, > - * aside from the short-lived offset, that becomes history at > - * the next event sched-in and therefore isn't useful. > - * The userspace that needs to copy out AUX data in overwrite > - * mode should know to use user_page::aux_head for the actual > - * offset. So, from now on we don't output AUX records that > - * have *only* OVERWRITE flag set. > - */ > - > - if (handle->aux_flags & ~(u64)PERF_AUX_FLAG_OVERWRITE) > - perf_event_aux_event(handle->event, aux_head, size, > - handle->aux_flags); > - } > + /* > + * Only send RECORD_AUX if we have something useful to communicate > + * > + * Note: the OVERWRITE records by themselves are not considered > + * useful, as they don't communicate any *new* information, > + * aside from the short-lived offset, that becomes history at > + * the next event sched-in and therefore isn't useful. > + * The userspace that needs to copy out AUX data in overwrite > + * mode should know to use user_page::aux_head for the actual > + * offset. So, from now on we don't output AUX records that > + * have *only* OVERWRITE flag set. > + */ > + if (size || (handle->aux_flags & ~(u64)PERF_AUX_FLAG_OVERWRITE)) > + perf_event_aux_event(handle->event, aux_head, size, > + handle->aux_flags); Acked-by: Will Deacon Assuming this will make it into 5.1 as a fix? Will