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,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 DB2A6C65C20 for ; Mon, 8 Oct 2018 14:46:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 964B8204FD for ; Mon, 8 Oct 2018 14:46:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 964B8204FD 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 S1726481AbeJHV6q (ORCPT ); Mon, 8 Oct 2018 17:58:46 -0400 Received: from mga04.intel.com ([192.55.52.120]:22551 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726278AbeJHV6q (ORCPT ); Mon, 8 Oct 2018 17:58:46 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 08 Oct 2018 07:42:39 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,357,1534834800"; d="scan'208";a="263870186" Received: from linux.intel.com ([10.54.29.200]) by orsmga005.jf.intel.com with ESMTP; 08 Oct 2018 07:42:22 -0700 Received: from [10.252.30.144] (abudanko-mobl.ccr.corp.intel.com [10.252.30.144]) by linux.intel.com (Postfix) with ESMTP id 9EEC65801E6; Mon, 8 Oct 2018 07:42:20 -0700 (PDT) Subject: Re: [PATCH v11 2/3]: perf record: enable asynchronous trace writing To: Jiri Olsa Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Namhyung Kim , Andi Kleen , linux-kernel References: <7d42aa80-8e69-44e4-b963-e8ef89df2099@linux.intel.com> <31b0ae5f-e1b5-4255-11af-46c8ebe8e2be@linux.intel.com> <20181008105254.GG17270@krava> <20181008125310.GF18757@krava> From: Alexey Budankov Organization: Intel Corp. Message-ID: Date: Mon, 8 Oct 2018 17:42:18 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181008125310.GF18757@krava> Content-Type: text/plain; charset=utf-8 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 Hi, On 08.10.2018 15:53, Jiri Olsa wrote: > On Mon, Oct 08, 2018 at 03:24:31PM +0300, Alexey Budankov wrote: >> Hi, >> >> On 08.10.2018 13:52, Jiri Olsa wrote: >>> On Mon, Oct 08, 2018 at 09:17:11AM +0300, Alexey Budankov wrote: >> >>>> +#ifdef HAVE_AIO_SUPPORT >>>> + off = lseek(trace_fd, 0, SEEK_CUR); >>>> +#endif >>> >>> I'm still little puzzled why we need to do this, >>> when the aio write takes the offset value, but >> >> pwrite() syscall [1] which is the base for aio_write() doesn't >> advance file pos value so it requires to be calculated and >> updated by callers of aio_write() API. > > ok, so aio_write does not need the offset to be updated, > who needs it then? aio_write() needs this offset as an input parameter. aio_write() gets offset as a part of cblock object. Adjacent aio_write() records should not overlap in the trace file so off value is incremented by size in every loop iteration after successful aio_write() call. Thanks, Alexey > > jirka >