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 359B6C433F4 for ; Mon, 27 Aug 2018 09:20:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D89CB208E8 for ; Mon, 27 Aug 2018 09:20:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D89CB208E8 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 S1726934AbeH0NGp (ORCPT ); Mon, 27 Aug 2018 09:06:45 -0400 Received: from mga03.intel.com ([134.134.136.65]:57710 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726802AbeH0NGo (ORCPT ); Mon, 27 Aug 2018 09:06:44 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Aug 2018 02:20:53 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,294,1531810800"; d="scan'208";a="83688255" Received: from linux.intel.com ([10.54.29.200]) by fmsmga004.fm.intel.com with ESMTP; 27 Aug 2018 02:20:53 -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 25D555803DA; Mon, 27 Aug 2018 02:20:50 -0700 (PDT) Subject: Re: [PATCH v1 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: <2db359cc-dc5d-c00e-a42a-12a2e9da80b7@linux.intel.com> <20180826214856.GA24518@krava> From: Alexey Budankov Organization: Intel Corp. Message-ID: <3a8286ff-124f-fb56-1d1c-5d5e1f3b8512@linux.intel.com> Date: Mon, 27 Aug 2018 12:20:50 +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: <20180826214856.GA24518@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 0:48, Jiri Olsa wrote: > On Tue, Aug 21, 2018 at 11:27:03AM +0300, Alexey Budankov wrote: > > SNIP > >> -static int record__pushfn(void *to, void *bf, size_t size) >> +static int record__pushfn(void *to, void *bf, size_t size, off_t off) >> { >> struct record *rec = to; >> + struct perf_mmap *map = bf; >> >> rec->samples++; >> - return record__write(rec, bf, size); >> + return record__aio_write(rec->session->data->file.fd, &map->cblock, >> + map->data, size, off); >> } >> >> static volatile int done; >> @@ -528,13 +530,85 @@ static struct perf_event_header finished_round_event = { >> .type = PERF_RECORD_FINISHED_ROUND, >> }; >> >> +static int record__mmap_read_sync(int trace_fd, struct aiocb **cblocks, >> + int cblocks_size, struct record *rec) >> +{ >> + size_t rem; >> + ssize_t size; >> + off_t rem_off; >> + int i, aio_ret, aio_errno, do_suspend; >> + struct perf_mmap *md; >> + struct timespec timeout0 = { 0, 0 }; >> + struct timespec timeoutS = { 0, 1000 * 500 * 1 }; >> + >> + if (!cblocks_size) >> + return 0; >> + >> + do { >> + do_suspend = 0; >> + nanosleep(&timeoutS, NULL); > > why the extra sleep in here and not sleeping through aio_suspend call? Yep. Good question. That requires explicit explanation: + /* aio_suspend() implementation inside glibc (as of v2.27) is + * intrusive and not just blocks waiting io requests completion + * but polls requests queue inducing context switches in perf + * tool process. When profiling in system wide mode with tracing + * context switches the trace may be polluted by context switches + * from the perf process and the trace size becomes about 3-5 + * times bigger than that of when writing the trace serially. + * To limit the volume of context switches from perf tool + * process nonsleep() call limits aio_suspend() + * polling till every half of the kernel timer tick which is + * usually 1ms (depends on CONFIG_HZ value). + */ > > jirka > >> + if (aio_suspend((const struct aiocb**)cblocks, cblocks_size, &timeout0)) { >> + if (errno == EAGAIN || errno == EINTR) { >> + do_suspend = 1; >> + continue; >> + } else { >> + pr_err("failed to sync perf data, error: %m\n"); > > SNIP >