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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 89CABC433E0 for ; Thu, 25 Jun 2020 19:32:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C4C720767 for ; Thu, 25 Jun 2020 19:32:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406582AbgFYTcg (ORCPT ); Thu, 25 Jun 2020 15:32:36 -0400 Received: from mga05.intel.com ([192.55.52.43]:51336 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406116AbgFYTcf (ORCPT ); Thu, 25 Jun 2020 15:32:35 -0400 IronPort-SDR: L87Y24AbTm1zSuo3jM9hq2lwaK+R+LuXj0tjK1R/Yxh4/A8s1zA/o48s3WyMuotBV73RUgCAMC F0OvuO0H4F5Q== X-IronPort-AV: E=McAfee;i="6000,8403,9663"; a="229771891" X-IronPort-AV: E=Sophos;i="5.75,280,1589266800"; d="scan'208";a="229771891" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Jun 2020 12:32:35 -0700 IronPort-SDR: etYHETo53L1uPh13M3zLNlnSPV2BuCw99dFxHIzzOhgBoNotpSxUwwXkOJDL8cbzRwOXGUCVVV jMYptsNm4wjw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,280,1589266800"; d="scan'208";a="479753275" Received: from linux.intel.com ([10.54.29.200]) by fmsmga005.fm.intel.com with ESMTP; 25 Jun 2020 12:32:35 -0700 Received: from [10.249.229.54] (abudanko-mobl.ccr.corp.intel.com [10.249.229.54]) by linux.intel.com (Postfix) with ESMTP id DD0915804B4; Thu, 25 Jun 2020 12:32:30 -0700 (PDT) Subject: Re: [PATCH v8 01/13] tools/libperf: avoid moving of fds at fdarray__filter() call To: Jiri Olsa Cc: Arnaldo Carvalho de Melo , Namhyung Kim , Alexander Shishkin , Peter Zijlstra , Ingo Molnar , Andi Kleen , linux-kernel References: <0781a077-aa82-5b4a-273e-c17372a72b93@linux.intel.com> <3d36dc7a-4249-096c-7554-80e6d290eac5@linux.intel.com> <20200625171405.GL2719003@krava> From: Alexey Budankov Organization: Intel Corp. Message-ID: <688910f3-289e-d63e-79e3-0a17a6df0e9e@linux.intel.com> Date: Thu, 25 Jun 2020 22:32:29 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200625171405.GL2719003@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 On 25.06.2020 20:14, Jiri Olsa wrote: > On Wed, Jun 24, 2020 at 08:19:32PM +0300, Alexey Budankov wrote: >> >> On 17.06.2020 11:35, Alexey Budankov wrote: >>> >>> Skip fds with zeroed revents field from count and avoid fds moving >>> at fdarray__filter() call so fds indices returned by fdarray__add() >>> call stay the same and can be used for direct access and processing >>> of fd revents status field at entries array of struct fdarray object. >>> >>> Signed-off-by: Alexey Budankov >>> --- >>> tools/lib/api/fd/array.c | 11 +++++------ >>> tools/perf/tests/fdarray.c | 20 ++------------------ >>> 2 files changed, 7 insertions(+), 24 deletions(-) >>> >>> diff --git a/tools/lib/api/fd/array.c b/tools/lib/api/fd/array.c >>> index 58d44d5eee31..97843a837370 100644 >>> --- a/tools/lib/api/fd/array.c >>> +++ b/tools/lib/api/fd/array.c >>> @@ -93,22 +93,21 @@ int fdarray__filter(struct fdarray *fda, short revents, >>> return 0; >>> >>> for (fd = 0; fd < fda->nr; ++fd) { >>> + if (!fda->entries[fd].revents) >>> + continue; >>> + >> >> So it looks like this condition also filters out non signaling events fds, not only >> control and others fds, and this should be somehow avoided so such event related fds >> would be counted. Several options have been proposed so far: >> >> 1) Explicit typing of fds via API extension and filtering based on the types: >> a) with separate fdarray__add_stat() call >> b) with type arg of existing fdarray__add() call >> c) various memory management design is possible >> >> 2) Playing tricks with fd positions inside entries and assumptions on fdarray API calls ordering >> - looks more like a hack than a designed solution >> >> 3) Rewrite of fdarray class to allocate separate object for every added fds >> - can be replaced with nonscrewing of fds by __filter() >> >> 4) Distinct between fds types at fdarray__filter() using .revents == 0 condition >> - seems to have corner cases and thus not applicable >> >> 5) Extension of fdarray__poll(, *arg_ptr, arg_size) with arg of fds array to atomically poll >> on fdarray_add()-ed fds and external arg fds and then external arg fds processing >> >> 6) Rewrite of fdarray class on epoll() call basis >> - introduces new scalability restrictions for Perf tool > > hum, how many fds for polling do you expect in your workloads? Currently it is several hundreds so default of 1K is easily hit and "Profile a Large Number of PMU Events on Multi-Core Systems" section [1] recommends: soft nofile 65535 hard nofile 65535 for for /etc/security/limits.conf settings. ~Alexey [1] https://software.intel.com/content/www/us/en/develop/documentation/vtune-cookbook/top/configuration-recipes/profiling-hardware-without-sampling-drivers.html > > jirka >