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=-12.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_PASS 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 B8EAEC43381 for ; Fri, 29 Mar 2019 20:35:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6D9DB2184C for ; Fri, 29 Mar 2019 20:35:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730181AbfC2Uf0 (ORCPT ); Fri, 29 Mar 2019 16:35:26 -0400 Received: from terminus.zytor.com ([198.137.202.136]:60335 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730014AbfC2Uf0 (ORCPT ); Fri, 29 Mar 2019 16:35:26 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id x2TKZJWg3937454 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Fri, 29 Mar 2019 13:35:19 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id x2TKZHUl3937448; Fri, 29 Mar 2019 13:35:17 -0700 Date: Fri, 29 Mar 2019 13:35:17 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Adrian Hunter Message-ID: Cc: hpa@zytor.com, tglx@linutronix.de, adrian.hunter@intel.com, mingo@kernel.org, jolsa@redhat.com, acme@redhat.com, linux-kernel@vger.kernel.org Reply-To: hpa@zytor.com, mingo@kernel.org, adrian.hunter@intel.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, acme@redhat.com, jolsa@redhat.com In-Reply-To: <20190325135135.18348-1-adrian.hunter@intel.com> References: <20190325135135.18348-1-adrian.hunter@intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/urgent] perf intel-pt: Fix TSC slip Git-Commit-ID: f3b4e06b3bda759afd042d3d5fa86bea8f1fe278 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: f3b4e06b3bda759afd042d3d5fa86bea8f1fe278 Gitweb: https://git.kernel.org/tip/f3b4e06b3bda759afd042d3d5fa86bea8f1fe278 Author: Adrian Hunter AuthorDate: Mon, 25 Mar 2019 15:51:35 +0200 Committer: Arnaldo Carvalho de Melo CommitDate: Thu, 28 Mar 2019 14:31:55 -0300 perf intel-pt: Fix TSC slip A TSC packet can slip past MTC packets so that the timestamp appears to go backwards. One estimate is that can be up to about 40 CPU cycles, which is certainly less than 0x1000 TSC ticks, but accept slippage an order of magnitude more to be on the safe side. Signed-off-by: Adrian Hunter Cc: Jiri Olsa Cc: stable@vger.kernel.org Fixes: 79b58424b821c ("perf tools: Add Intel PT support for decoding MTC packets") Link: http://lkml.kernel.org/r/20190325135135.18348-1-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/intel-pt-decoder/intel-pt-decoder.c | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-) diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c index 6e03db142091..872fab163585 100644 --- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c +++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c @@ -251,19 +251,15 @@ struct intel_pt_decoder *intel_pt_decoder_new(struct intel_pt_params *params) if (!(decoder->tsc_ctc_ratio_n % decoder->tsc_ctc_ratio_d)) decoder->tsc_ctc_mult = decoder->tsc_ctc_ratio_n / decoder->tsc_ctc_ratio_d; - - /* - * Allow for timestamps appearing to backwards because a TSC - * packet has slipped past a MTC packet, so allow 2 MTC ticks - * or ... - */ - decoder->tsc_slip = multdiv(2 << decoder->mtc_shift, - decoder->tsc_ctc_ratio_n, - decoder->tsc_ctc_ratio_d); } - /* ... or 0x100 paranoia */ - if (decoder->tsc_slip < 0x100) - decoder->tsc_slip = 0x100; + + /* + * A TSC packet can slip past MTC packets so that the timestamp appears + * to go backwards. One estimate is that can be up to about 40 CPU + * cycles, which is certainly less than 0x1000 TSC ticks, but accept + * slippage an order of magnitude more to be on the safe side. + */ + decoder->tsc_slip = 0x10000; intel_pt_log("timestamp: mtc_shift %u\n", decoder->mtc_shift); intel_pt_log("timestamp: tsc_ctc_ratio_n %u\n", decoder->tsc_ctc_ratio_n);