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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 1A517C43381 for ; Wed, 27 Mar 2019 14:42:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D65622087C for ; Wed, 27 Mar 2019 14:42:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728708AbfC0Omi (ORCPT ); Wed, 27 Mar 2019 10:42:38 -0400 Received: from mga09.intel.com ([134.134.136.24]:49005 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725764AbfC0Omi (ORCPT ); Wed, 27 Mar 2019 10:42:38 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Mar 2019 07:42:22 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,277,1549958400"; d="scan'208";a="144330923" Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.7.201.137]) by FMSMGA003.fm.intel.com with ESMTP; 27 Mar 2019 07:42:22 -0700 Received: by tassilo.localdomain (Postfix, from userid 1000) id 248173015ED; Wed, 27 Mar 2019 07:42:22 -0700 (PDT) Date: Wed, 27 Mar 2019 07:42:22 -0700 From: Andi Kleen To: "Liang, Kan" Cc: peterz@infradead.org, acme@kernel.org, mingo@redhat.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, jolsa@kernel.org, eranian@google.com, alexander.shishkin@linux.intel.com Subject: Re: [PATCH V4 04/23] perf/x86/intel: Support adaptive PEBSv4 Message-ID: <20190327144222.GT18020@tassilo.jf.intel.com> References: <20190326160901.4887-1-kan.liang@linux.intel.com> <20190326160901.4887-5-kan.liang@linux.intel.com> <20190326222441.GP18020@tassilo.jf.intel.com> <9d267395-fda8-d111-52a2-e7cdcdf7d24b@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9d267395-fda8-d111-52a2-e7cdcdf7d24b@linux.intel.com> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > We need to call perf_event_overflow() for the last record of each event. > It's hard to detect which record is the last record of the event with one > pass walking. > > Also, I'm not sure how much we can save with one pass walking. The > optimization should only benefit large PEBS. The total number of records for > large PEBS should not be huge. > I will evaluate the performance impact of one pass walking. If there is > observed performance improvement, I will submit a separate patch later. > > For now, I think we can still use the mature two pass walking method. Okay sounds reasonable to keep it then. Thanks, -Andi