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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by aws-us-west-2-korg-lkml-1.web.codeaurora.org (Postfix) with ESMTP id 1EB65C5CFC1 for ; Fri, 15 Jun 2018 08:24:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D2051208B5 for ; Fri, 15 Jun 2018 08:24:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D2051208B5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756041AbeFOIYx (ORCPT ); Fri, 15 Jun 2018 04:24:53 -0400 Received: from mga18.intel.com ([134.134.136.126]:5053 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755847AbeFOIYw (ORCPT ); Fri, 15 Jun 2018 04:24:52 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 15 Jun 2018 01:24:52 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,226,1526367600"; d="scan'208";a="237381833" Received: from yjin15-mobl.ccr.corp.intel.com (HELO [10.239.161.30]) ([10.239.161.30]) by fmsmga005.fm.intel.com with ESMTP; 15 Jun 2018 01:24:49 -0700 Subject: Re: [PATCH v1 0/2] perf: Drop leaked kernel samples To: Peter Zijlstra Cc: acme@kernel.org, jolsa@kernel.org, mingo@redhat.com, alexander.shishkin@linux.intel.com, me@kylehuey.com, Linux-kernel@vger.kernel.org, vincent.weaver@maine.edu, will.deacon@arm.com, eranian@google.com, namhyung@kernel.org, ak@linux.intel.com, kan.liang@intel.com, yao.jin@intel.com References: <1529057003-2212-1-git-send-email-yao.jin@linux.intel.com> <20180615074504.GA2458@hirez.programming.kicks-ass.net> <11958be5-dc05-611b-6839-f1f6903c7ca8@linux.intel.com> <20180615081223.GB2458@hirez.programming.kicks-ass.net> From: "Jin, Yao" Message-ID: Date: Fri, 15 Jun 2018 16:24:49 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180615081223.GB2458@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/15/2018 4:12 PM, Peter Zijlstra wrote: > On Fri, Jun 15, 2018 at 04:01:45PM +0800, Jin, Yao wrote: > >> Bring more overhead to kernel if we zero the bits considering the number of >> leaked samples may be not too small? > > Keeping the samples at least allows you to know how many samples > happened and such things. > Yeah, agree, but a little bit overhead ... >> And the skid information may be interesting (see example of hitting on >> page_fault in previous mail). If we zero it, we will not know. > > If you throw them out the window you also don't know, do you? > Yes, default I can't know that window. I have to use sysctl to enable. Thanks Jin Yao