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=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,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 15064C43381 for ; Mon, 25 Mar 2019 14:50:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D3C3420811 for ; Mon, 25 Mar 2019 14:50:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="sbBwAzPZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729422AbfCYOud (ORCPT ); Mon, 25 Mar 2019 10:50:33 -0400 Received: from mail-qt1-f193.google.com ([209.85.160.193]:36579 "EHLO mail-qt1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729273AbfCYOu1 (ORCPT ); Mon, 25 Mar 2019 10:50:27 -0400 Received: by mail-qt1-f193.google.com with SMTP id y36so10589672qtb.3 for ; Mon, 25 Mar 2019 07:50:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=eeX2FGRu0IMKLo1z4mtpqCiXxn6OktfznzkPx63ejRk=; b=sbBwAzPZq0IU6Zzk4XbJagNswHCk4sHkP9gMZkIWOsdthzdPbKlvhDLhkj1f/ElluO baDWXAFU/2UZEPYXxnqUztBhwh63feTxtbpazIfvt0iJAPoeeV+agdUB7MyUffO0ucjb N7z2y/F+pBNLdt+yiubr2opvfbXhIP7mU2SDv8x0xYqqx4SPENHckhbNzwpr33yd3dfv SxYrtesWWwIh87wcGFQvz29YHuHXZPEJ62gIGGyAumqlHru6JidT6ed0d97Do2skdixB nHx+I761ieitkrUlgqjkPGidKD8IG25N0yYtl6LrYuIa0vB3bC9bfyFTeJ/+tvp6+6z+ YSIw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=eeX2FGRu0IMKLo1z4mtpqCiXxn6OktfznzkPx63ejRk=; b=ju5AndwFNS0LUJj3SFt5nSCvEr/E3cGgITR/bvsiP27ozp732qRKXRZJGRi6azURf2 uM35+p/j2RL8ZhPtklGgpNaDH2fSFf29aGEkvPk1iZ5LpqEDevgopY4GcAtfwJ/4xK6V eyhMejUnHzO4QNhyaZjxNNPsyuGPO2I4IRRb0Jrdz0Y2rFR1Rr7ohTzfNIWLzsEUg8Fh RdX8JNZWQap1iAGfO3LrehBODhZ0981I2ZnLK1050YGXpieNztBXQw84hZCn5O/cFL0r r9l39V/yhpYW/PEgJUV6MFIfH0BqlvUcjrigXNKtuZ9YybvqIoei1EnAAMdW53Orcb/V HZbw== X-Gm-Message-State: APjAAAVkmjAj9iw/ImNJML+LcIS7eChB+V/WMs46kpmH22Vj7txI8nWo +4rBj9hDfPGvRvJLFvM4prcslx12 X-Google-Smtp-Source: APXvYqwaGd8MT5iHlTM3FPnHzcdhIVabDsgMKrZuGCPIgwTd4n14LtOBF2s1E8mVssJnrcaPOa2Xjg== X-Received: by 2002:ac8:2d56:: with SMTP id o22mr21394021qta.321.1553525425560; Mon, 25 Mar 2019 07:50:25 -0700 (PDT) Received: from quaco.ghostprotocols.net ([190.15.121.82]) by smtp.gmail.com with ESMTPSA id t69sm8873879qke.38.2019.03.25.07.50.22 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 25 Mar 2019 07:50:23 -0700 (PDT) From: Arnaldo Carvalho de Melo X-Google-Original-From: Arnaldo Carvalho de Melo Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 9169E4039C; Mon, 25 Mar 2019 11:50:19 -0300 (-03) Date: Mon, 25 Mar 2019 11:50:19 -0300 To: Adrian Hunter Cc: Jiri Olsa , linux-kernel@vger.kernel.org Subject: Re: [RESEND PATCH] perf intel-pt: Fix TSC slip Message-ID: <20190325145019.GC6231@kernel.org> References: <20190325135135.18348-1-adrian.hunter@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190325135135.18348-1-adrian.hunter@intel.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Mon, Mar 25, 2019 at 03:51:35PM +0200, Adrian Hunter escreveu: > 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. thanks, applied to perf/urgent. - Arnaldo > Signed-off-by: Adrian Hunter > Fixes: 79b58424b821c ("perf tools: Add Intel PT support for decoding MTC packets") > Cc: stable@vger.kernel.org > --- > .../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); > -- > 2.17.1 -- - Arnaldo