From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751790AbcEQHbl (ORCPT ); Tue, 17 May 2016 03:31:41 -0400 Received: from mga14.intel.com ([192.55.52.115]:22980 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750875AbcEQHbk (ORCPT ); Tue, 17 May 2016 03:31:40 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,324,1459839600"; d="scan'208";a="968500196" From: Alexander Shishkin To: stable@vger.kernel.org Cc: gregkh@linuxfoundation.org, jolsa@redhat.com, tglx@linutronix.de, torvalds@linux-foundation.org, vincent.weaver@maine.edu, bp@alien8.de, hpa@zytor.com, eranian@google.com, markus.t.metzger@intel.com, stable@vger.kernel.org, acme@redhat.com, mingo@kernel.org, linux-kernel@vger.kernel.org, acme@infradead.org, peterz@infradead.org Subject: Re: [tip:perf/urgent] perf/x86/intel/pt: Generate PMI in the STOP region as well In-Reply-To: References: <1462886313-13660-2-git-send-email-alexander.shishkin@linux.intel.com> User-Agent: Notmuch/0.21 (http://notmuchmail.org) Emacs/24.5.1 (x86_64-pc-linux-gnu) Date: Tue, 17 May 2016 10:31:26 +0300 Message-ID: <87a8jpta29.fsf@ashishki-desk.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org tip-bot for Alexander Shishkin writes: > Commit-ID: ab92b232ae05c382c3df0e3d6a5c6d16b639ac8c > Gitweb: http://git.kernel.org/tip/ab92b232ae05c382c3df0e3d6a5c6d16b639ac8c > Author: Alexander Shishkin > AuthorDate: Tue, 10 May 2016 16:18:32 +0300 > Committer: Ingo Molnar > CommitDate: Thu, 12 May 2016 14:45:59 +0200 > > perf/x86/intel/pt: Generate PMI in the STOP region as well > > Currently, the PT driver always sets the PMI bit one region (page) before > the STOP region so that we can wake up the consumer before we run out of > room in the buffer and have to disable the event. However, we also need > an interrupt in the last output region, so that we actually get to disable > the event (if no more room from new data is available at that point), > otherwise hardware just quietly refuses to start, but the event is > scheduled in and we end up losing trace data till the event gets removed. > > For a cpu-wide event it is even worse since there may not be any > re-scheduling at all and no chance for the ring buffer code to notice > that its buffer is filled up and the event needs to be disabled (so that > the consumer can re-enable it when it finishes reading the data out). In > other words, all the trace data will be lost after the buffer gets filled > up. > > This patch makes PT also generate a PMI when the last output region is > full. > > Reported-by: Markus Metzger > Signed-off-by: Alexander Shishkin > Signed-off-by: Peter Zijlstra (Intel) > Cc: Can we also have this one queued up for stable 4.4 and 4.5? Thanks, -- Alex