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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 D94D5C433E0 for ; Wed, 3 Jun 2020 17:00:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD6402081A for ; Wed, 3 Jun 2020 17:00:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726221AbgFCRAU (ORCPT ); Wed, 3 Jun 2020 13:00:20 -0400 Received: from mga06.intel.com ([134.134.136.31]:53260 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725961AbgFCRAS (ORCPT ); Wed, 3 Jun 2020 13:00:18 -0400 IronPort-SDR: 6g0urmMDxlevPpXxA0YVEKiSqyfFw57LKIiUGO3bvZAF8DmVCaexnY1lz5M8TKykNjEKTniOEJ hx7yCQmqibAw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Jun 2020 10:00:17 -0700 IronPort-SDR: nHx2z2msyOw8QxBH6B4KKm8vReGfEqeX+xjzqGcmFuJSU+sJTAWKEOWof2IWMvv3suXUvojTJg YZA4IHh1t3fQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,468,1583222400"; d="scan'208";a="312659773" Received: from linux.intel.com ([10.54.29.200]) by FMSMGA003.fm.intel.com with ESMTP; 03 Jun 2020 10:00:16 -0700 Received: from [10.249.225.188] (abudanko-mobl.ccr.corp.intel.com [10.249.225.188]) by linux.intel.com (Postfix) with ESMTP id CDC875800E3; Wed, 3 Jun 2020 10:00:13 -0700 (PDT) Subject: Re: [PATCH v6 01/13] tools/libperf: introduce notion of static polled file descriptors To: Adrian Hunter Cc: Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim , Alexander Shishkin , Peter Zijlstra , Ingo Molnar , Andi Kleen , linux-kernel References: <40643542-6676-e0bc-2d10-165dfde41e29@linux.intel.com> <33c91520-7040-bd6b-b176-004ddbec2a63@intel.com> <363DA0ED52042842948283D2FC38E464B4151F86@IRSMSX106.ger.corp.intel.com> <40d44cd8-ecdb-53c9-99f8-1737e04c84ff@linux.intel.com> <2d264b14-7f60-9d43-2d52-3709c7295c4a@intel.com> From: Alexey Budankov Organization: Intel Corp. Message-ID: <5a01eace-e502-c78c-7ab8-a298b0e18c08@linux.intel.com> Date: Wed, 3 Jun 2020 20:00:12 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.1 MIME-Version: 1.0 In-Reply-To: <2d264b14-7f60-9d43-2d52-3709c7295c4a@intel.com> 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 03.06.2020 18:53, Adrian Hunter wrote: > On 3/06/20 3:52 pm, Alexey Budankov wrote: >> >> On 03.06.2020 15:30, Hunter, Adrian wrote: >>> >>> >>>> -----Original Message----- >>>> From: Hunter, Adrian >>>> Sent: Wednesday, June 3, 2020 3:24 PM >>>> To: Alexey Budankov >>>> Cc: Arnaldo Carvalho de Melo ; Jiri Olsa >>>> ; Namhyung Kim ; Alexander >>>> Shishkin ; Peter Zijlstra >>>> ; Ingo Molnar ; Andi Kleen >>>> ; linux-kernel >>>> Subject: Re: [PATCH v6 01/13] tools/libperf: introduce notion of static polled >>>> file descriptors >>>> >>>> On 3/06/20 3:01 pm, Alexey Budankov wrote: >>>>> Hi, >>>>> >>>>> On 03.06.2020 14:38, Adrian Hunter wrote: >>>>>> On 1/06/20 11:05 pm, Alexey Budankov wrote: >>>>>>> >>>>>>> Implement adding of file descriptors by fdarray__add_stat() to >>>>>>> fix-sized (currently 1) stat_entries array located at struct fdarray. >>>>>>> Append added file descriptors to the array used by poll() syscall >>>>>>> during fdarray__poll() call. Copy poll() result of the added >>>>>>> descriptors from the array back to the storage for separate analysis. >>>>>> >>>>>> Why not instead call evlist__add_pollfd() before other fds are added, >>>>>> so the fda->entries[] position is always fixed. Then this patch is not >>>> needed. >>>>> >>>>> It then will block event consumption loop, at least in record mode, >>>>> due to change sin initial assumptions behind fdarray__filter(). So >>>>> extension of the API with 'static' fds looks safer w.r.t. possible >>>>> functional regressions at the same time extending the API with ability >>>>> to atomically wait for (poll()) not only event fds but also any other fds >>>> during monitoring. >>>> >>>> So make fdarray__filter() return the number of filterable fds remaining. >>>> >>> >>> >>> Or perhaps simpler, compare the return value to the number of fds that are known not to be filterable >> >> Well, various implementations are for sure possible but the proposed design >> avoids implicit code assumptions and dependency on API calls order as in API >> implementation as in client code and that is why it's been proposed this way. >> > > The dependencies are confined one function, namely __cmd_record(), it is > simpler, and avoids the inelegant changes to fdarray__poll(). As far the changes don't cause regressions and serve their purpose well they are acceptable.