From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=9Qwj=MR=vger.kernel.org=linux-kernel-owner@kernel.org>
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 2C526C00449
	for <linux-kernel@archiver.kernel.org>; Fri,  5 Oct 2018 15:54:55 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
	by mail.kernel.org (Postfix) with ESMTP id E0B0E2084D
	for <linux-kernel@archiver.kernel.org>; Fri,  5 Oct 2018 15:54:54 +0000 (UTC)
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E0B0E2084D
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 S1728778AbeJEWyK (ORCPT
        <rfc822;linux-kernel@archiver.kernel.org>);
        Fri, 5 Oct 2018 18:54:10 -0400
Received: from mga01.intel.com ([192.55.52.88]:18504 "EHLO mga01.intel.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1727572AbeJEWyK (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 5 Oct 2018 18:54:10 -0400
X-Amp-Result: SKIPPED(no attachment in message)
X-Amp-File-Uploaded: False
Received: from fmsmga006.fm.intel.com ([10.253.24.20])
  by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Oct 2018 08:54:52 -0700
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.54,345,1534834800"; 
   d="scan'208";a="269804779"
Received: from linux.intel.com ([10.54.29.200])
  by fmsmga006.fm.intel.com with ESMTP; 05 Oct 2018 08:53:21 -0700
Received: from [10.125.251.251] (abudanko-mobl.ccr.corp.intel.com [10.125.251.251])
        by linux.intel.com (Postfix) with ESMTP id 7189058038C;
        Fri,  5 Oct 2018 08:53:19 -0700 (PDT)
Subject: Re: [PATCH v9 2/3]: perf record: enable asynchronous trace writing
From:   Alexey Budankov <alexey.budankov@linux.intel.com>
To:     Namhyung Kim <namhyung@kernel.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>, Andi Kleen <ak@linux.intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>, kernel-team@lge.com
References: <ded47c34-9e92-6bd2-9522-a927a7237011@linux.intel.com>
 <5ed78452-ff2b-dfe5-ec29-888971cb4b55@linux.intel.com>
 <20181005071615.GC3768@sejong>
 <dc944fcf-cbb6-9b88-bc1c-606eb027a6ac@linux.intel.com>
 <20181005084854.GE3768@sejong>
 <4ee1c347-674b-ac61-65cf-55fb71a7cc2b@linux.intel.com>
 <20181005105557.GF3768@sejong>
 <c5129bc1-1e69-0fcc-c552-9bda51886bcf@linux.intel.com>
Organization: Intel Corp.
Message-ID: <558ec0ad-7083-e4ed-e6bb-9b90c86b20bf@linux.intel.com>
Date:   Fri, 5 Oct 2018 18:53:17 +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: <c5129bc1-1e69-0fcc-c552-9bda51886bcf@linux.intel.com>
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: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi,
On 05.10.2018 14:50, Alexey Budankov wrote:<SNIP>
> 
> According to docs [1] ftruncate() does not advance file pos 
> which is essential here.
> 

Ideally, the both lseek() syscalls in every loop iteration can be
replaced by the only two syscalls just before and after the loop and
advancing *in-flight* off file pos value at perf_mmap__aio_push() 
after every successful record__aio_pushfn().

Thanks,
Alexey