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 485C0C00449 for ; Fri, 5 Oct 2018 08:31:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 05ADB208E7 for ; Fri, 5 Oct 2018 08:31:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 05ADB208E7 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 S1728668AbeJEP24 (ORCPT ); Fri, 5 Oct 2018 11:28:56 -0400 Received: from mga18.intel.com ([134.134.136.126]:61934 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728451AbeJEP2z (ORCPT ); Fri, 5 Oct 2018 11:28:55 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Oct 2018 01:31:15 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,343,1534834800"; d="scan'208";a="92439711" Received: from linux.intel.com ([10.54.29.200]) by fmsmga002.fm.intel.com with ESMTP; 05 Oct 2018 01:31:15 -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 E797458038C; Fri, 5 Oct 2018 01:31:12 -0700 (PDT) Subject: Re: [PATCH v9 2/3]: perf record: enable asynchronous trace writing To: Namhyung Kim Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Andi Kleen , linux-kernel , kernel-team@lge.com References: <5ed78452-ff2b-dfe5-ec29-888971cb4b55@linux.intel.com> <20181005071615.GC3768@sejong> From: Alexey Budankov Organization: Intel Corp. Message-ID: Date: Fri, 5 Oct 2018 11:31:11 +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: <20181005071615.GC3768@sejong> 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 05.10.2018 10:16, Namhyung Kim wrote: > On Wed, Oct 03, 2018 at 07:12:10PM +0300, Alexey Budankov wrote: >> +static void record__aio_sync(struct perf_mmap *md) >> +{ >> + struct aiocb *cblock = &md->cblock; >> + struct timespec timeout = { 0, 1000 * 1000 * 1 }; // 1ms >> + >> + do { >> + if (cblock->aio_fildes == -1 || record__aio_complete(md, cblock)) >> + return; >> + >> + while (aio_suspend((const struct aiocb**)&cblock, 1, &timeout)) { >> + if (!(errno == EAGAIN || errno == EINTR)) >> + pr_err("failed to sync perf data, error: %m\n"); > > Is there somthing we can do in this error case? Any chance it gets > stuck in the loop? Not really. Currently, in glibc, it can block on a mutex only. > > >> + } >> + } while (1); >> +} >> + >> +static int record__aio_pushfn(void *to, struct aiocb *cblock, void *bf, size_t size) >> +{ >> + off_t off; >> + struct record *rec = to; >> + int ret, trace_fd = rec->session->data->file.fd; >> + >> + rec->samples++; >> + >> + off = lseek(trace_fd, 0, SEEK_CUR); >> + lseek(trace_fd, off + size, SEEK_SET); > > It'd be nice if these lseek() could be removed and use > rec->bytes_written instead. Well, this could be implemented like this avoiding lseek() in else branch: off = lseek(trace_fd, 0, SEEK_CUR); ret = record__aio_write(cblock, trace_fd, bf, size, off); if (!ret) { lseek(trace_fd, off + size, SEEK_SET); rec->bytes_written += size; if (switch_output_size(rec)) trigger_hit(&switch_output_trigger); } > > >> + ret = record__aio_write(cblock, trace_fd, bf, size, off); >> + if (!ret) { >> + rec->bytes_written += size; >> + >> + if (switch_output_size(rec)) >> + trigger_hit(&switch_output_trigger); > > Doesn't it need the _sync() before the trigger? Maybe it should be > moved to record__mmap_read_evlist() or so.. Currently trigger just updates variable state. The state is then checked thru separate API at __cmd_record() where record__mmap_read_sync() is called prior switching to a new trace file or finishing collection. >> >> if (map->base) { >> +#ifndef HAVE_AIO_SUPPORT >> if (perf_mmap__push(map, rec, record__pushfn) != 0) { >> rc = -1; >> goto out; >> } >> +#else >> + if (!rec->opts.nr_cblocks) { >> + if (perf_mmap__push(map, rec, record__pushfn) != 0) { >> + rc = -1; >> + goto out; >> + } >> + } else { >> + /* >> + * Call record__aio_sync() to wait till map->data buffer >> + * becomes available after previous aio write request. >> + */ >> + record__aio_sync(map); >> + if (perf_mmap__aio_push(map, rec, record__aio_pushfn) != 0) { >> + rc = -1; >> + goto out; >> + } >> + } >> +#endif > > If dummy aio functions are provided, the #ifdef can be removed and > just use the #else part assuming opts.nr_cblocks == 0. Yes, it looks a little bit cumbersome. Would this be more compact? if (map->base) { #ifdef HAVE_AIO_SUPPORT if (!rec->opts.nr_cblocks) { #endif if (perf_mmap__push(map, rec, record__pushfn) != 0) { rc = -1; goto out; } #ifdef HAVE_AIO_SUPPORT } else { int idx; /* * Call record__aio_sync() to wait till map->data buffer * becomes available after previous aio write request. */ idx = record__aio_sync(map, false); if (perf_mmap__aio_push(map, rec, idx, record__aio_pushfn) != 0) { rc = -1; goto out; } } #endif } Thanks, Alexey