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 8E7DFC433F5 for ; Mon, 27 Aug 2018 09:33:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4968420666 for ; Mon, 27 Aug 2018 09:33:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4968420666 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 S1727313AbeH0NTf (ORCPT ); Mon, 27 Aug 2018 09:19:35 -0400 Received: from mga02.intel.com ([134.134.136.20]:31423 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727098AbeH0NTf (ORCPT ); Mon, 27 Aug 2018 09:19:35 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Aug 2018 02:33:42 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,294,1531810800"; d="scan'208";a="66264628" Received: from linux.intel.com ([10.54.29.200]) by fmsmga008.fm.intel.com with ESMTP; 27 Aug 2018 02:33:11 -0700 Received: from [10.125.252.155] (abudanko-mobl.ccr.corp.intel.com [10.125.252.155]) by linux.intel.com (Postfix) with ESMTP id B12B65802AD; Mon, 27 Aug 2018 02:33:08 -0700 (PDT) Subject: Re: [PATCH v2 2/2]: 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 , linux-perf-users@vger.kernel.org References: <54cc11d7-3ef2-c856-052e-6e2c309ff743@linux.intel.com> <20180827083852.GF24695@krava> From: Alexey Budankov Organization: Intel Corp. Message-ID: Date: Mon, 27 Aug 2018 12:33:07 +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: <20180827083852.GF24695@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 27.08.2018 11:38, Jiri Olsa wrote: > On Thu, Aug 23, 2018 at 07:47:01PM +0300, Alexey Budankov wrote: > > SNIP > >> static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evlist, >> bool overwrite) >> { >> u64 bytes_written = rec->bytes_written; >> - int i; >> - int rc = 0; >> + int i, rc = 0; >> struct perf_mmap *maps; >> + int trace_fd = rec->session->data->file.fd; >> + struct aiocb **mmap_aio = rec->evlist->mmap_aio; >> + int mmap_aio_size = 0; >> + off_t off; >> >> if (!evlist) >> return 0; >> @@ -546,14 +620,17 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli >> if (overwrite && evlist->bkw_mmap_state != BKW_MMAP_DATA_PENDING) >> return 0; >> >> + off = lseek(trace_fd, 0, SEEK_CUR); >> + > > with async write, do we need to query/set the offset like this > all the time? It looks like we need it this way. Internally glibc AIO implements writes using pwrite64 syscall in our case. The sycall requires offset as a parameter and doesn't update file position on the completion. > > could we just keep/update the offset value in the 'struct perf_data_file' > and skip both lseek calls? Don't see how it is possible. offset is different for every enqeued write operation and write areas don't intersect for the whole writing loop. To know the final file position it is required to iterate thru the loop. > > jirka > > SNIP > >> >> + record__mmap_read_sync(trace_fd, mmap_aio, mmap_aio_size, rec); >> + >> + lseek(trace_fd, off, SEEK_SET); >> + >