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=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 8B132C00449 for ; Fri, 5 Oct 2018 08:48:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4711B208E7 for ; Fri, 5 Oct 2018 08:48:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4711B208E7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 S1728502AbeJEPql (ORCPT ); Fri, 5 Oct 2018 11:46:41 -0400 Received: from lgeamrelo11.lge.com ([156.147.23.51]:55213 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727236AbeJEPql (ORCPT ); Fri, 5 Oct 2018 11:46:41 -0400 Received: from unknown (HELO lgemrelse7q.lge.com) (156.147.1.151) by 156.147.23.51 with ESMTP; 5 Oct 2018 17:48:54 +0900 X-Original-SENDERIP: 156.147.1.151 X-Original-MAILFROM: namhyung@kernel.org Received: from unknown (HELO sejong) (10.177.227.17) by 156.147.1.151 with ESMTP; 5 Oct 2018 17:48:54 +0900 X-Original-SENDERIP: 10.177.227.17 X-Original-MAILFROM: namhyung@kernel.org Date: Fri, 5 Oct 2018 17:48:54 +0900 From: Namhyung Kim To: Alexey Budankov Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Andi Kleen , linux-kernel , kernel-team@lge.com Subject: Re: [PATCH v9 2/3]: perf record: enable asynchronous trace writing Message-ID: <20181005084854.GE3768@sejong> References: <5ed78452-ff2b-dfe5-ec29-888971cb4b55@linux.intel.com> <20181005071615.GC3768@sejong> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 05, 2018 at 11:31:11AM +0300, Alexey Budankov wrote: > Hi, 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. OK, I was thinking of a situation where the aio_suspend() keeps returning a same error code repeated.. > > > > > > >> + } > >> + } 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); > } Oh I meant the both like: off = rec->bytes_written; ret = record__aio_write(cblock, trace_fd, bf, size, off); if (!ret) { rec->bytes_written += size; ... > > > > > >> + 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? Why not exposing opts.nr_cblocks regardless of the #ifdef? It'll have 0 when it's not compiled in. Then it could be like below (assuming you have all the dummy aio funcitons): > > if (map->base) { > if (!rec->opts.nr_cblocks) { > if (perf_mmap__push(map, rec, record__pushfn) != 0) { > rc = -1; > goto out; > } > } 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; > } > } > } > Thanks, Namhyung