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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 48A29C11F66 for ; Tue, 29 Jun 2021 00:54:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2481961CF9 for ; Tue, 29 Jun 2021 00:54:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231718AbhF2A4g (ORCPT ); Mon, 28 Jun 2021 20:56:36 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:6017 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230090AbhF2A4f (ORCPT ); Mon, 28 Jun 2021 20:56:35 -0400 Received: from dggemv711-chm.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4GDQp909VtzXmFc; Tue, 29 Jun 2021 08:48:49 +0800 (CST) Received: from dggpemm000003.china.huawei.com (7.185.36.128) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Tue, 29 Jun 2021 08:54:06 +0800 Received: from [10.67.102.248] (10.67.102.248) by dggpemm000003.china.huawei.com (7.185.36.128) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Tue, 29 Jun 2021 08:54:06 +0800 Subject: Re: [PATCH] perf arm-spe: Fix incorrect sample timestamp in perf script To: Leo Yan CC: , , , , , , , , , , , , , , References: <20210626032115.16742-1-yangjihong1@huawei.com> <20210628014953.GA163942@leoy-ThinkPad-X240s> <75dac5f8-9c82-0db1-d362-44289dcaa206@huawei.com> <20210628040716.GC163942@leoy-ThinkPad-X240s> <2af84c69-8528-9c4a-f666-2dd660bcd966@huawei.com> <20210628072905.GB200044@leoy-ThinkPad-X240s> From: Yang Jihong Message-ID: <1bc5b36c-8138-4d14-c106-964682bf44dd@huawei.com> Date: Tue, 29 Jun 2021 08:53:55 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <20210628072905.GB200044@leoy-ThinkPad-X240s> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.102.248] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemm000003.china.huawei.com (7.185.36.128) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Leo, On 2021/6/28 15:29, Leo Yan wrote: > On Mon, Jun 28, 2021 at 02:30:56PM +0800, Yang Jihong wrote: >> Hello Leo, >> >> On 2021/6/28 12:07, Leo Yan wrote: >>> On Mon, Jun 28, 2021 at 11:45:07AM +0800, Yang Jihong wrote: >>> >>> [...] >>> >>>> The timestamp does not match. Each timestamp has a difference of >>>> 213.98296702 seconds. Is the command I executed wrong? >>> >>> I don't understand what's your meaning "a difference of 213.98296702 >>> seconds". >>> >>> But let me give an explaination with your below examples. You could >>> the command "perf script" outputs the timestamp 314938.859071370 which >>> is the kernel's timestamp, if using the command "perf script -D", it >>> outputs the value 31515284203839 which is the Arch timer's raw counter >>> value. >>> >>> In theory, the arch timer's counter is enabled at the very early >>> time before kernel's booting (e.g. bootloaders, UEFI, etc...). So for >>> the kernel's timestamp, it should calibrate the timestamp and reduce >>> the offset prior to the kernel's booting. I think this is the reason >>> why you observed 213.98296702 seconds difference (if compared with >>> your own patch?) >>> >>> If still see any issue, please let me know. Thanks a lot for the >>> testing! >>> >> Thanks for the very detailed explanation. >> To keep the correct relative time sequence between events in SPE and other >> events, we should use kernel timestamp instead of arch time. Therefore, we >> need to calibrate the time. Is this correct? > > Yes, correct! I see. Thank you for your answer.:) Jihong > . >