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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 8C014C433DF for ; Mon, 22 Jun 2020 12:11:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 61A09206FA for ; Mon, 22 Jun 2020 12:11:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="iZ8vfJs8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728097AbgFVML3 (ORCPT ); Mon, 22 Jun 2020 08:11:29 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:44379 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727956AbgFVML2 (ORCPT ); Mon, 22 Jun 2020 08:11:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592827887; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=E7hZu5TNzqp9fzhtFlbCxkjEMya/gyDFhXIk1StJTjc=; b=iZ8vfJs8iXqpuI7xh4wK2zbj8heHmRB7srntmcXDv6SUrV1v/zacf53+auJHvr7kvNpa6I qu+NN3JEAB85VR/H3bqFjO0gmDw00AI8aOxIRQaijTLeJdymbCkxh4fQCfJrg8bIp9LW9+ Fz6MvRHpAtkxt5fpjjz2ZCmWJARtiQ4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-38-yNlT5RR-P_CvcyD8SnZqyQ-1; Mon, 22 Jun 2020 08:11:25 -0400 X-MC-Unique: yNlT5RR-P_CvcyD8SnZqyQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DFCC0872FF1; Mon, 22 Jun 2020 12:11:23 +0000 (UTC) Received: from krava (unknown [10.40.193.171]) by smtp.corp.redhat.com (Postfix) with SMTP id F12A210013D2; Mon, 22 Jun 2020 12:11:21 +0000 (UTC) Date: Mon, 22 Jun 2020 14:11:20 +0200 From: Jiri Olsa To: Alexey Budankov Cc: Arnaldo Carvalho de Melo , Namhyung Kim , Alexander Shishkin , Peter Zijlstra , Ingo Molnar , Andi Kleen , linux-kernel Subject: Re: [PATCH v7 01/13] tools/libperf: introduce notion of static polled file descriptors Message-ID: <20200622121120.GA2584593@krava> References: <20200608084344.GA1520715@krava> <2d80a43a-54cf-3d12-92fd-066217c95d76@linux.intel.com> <20200608160758.GD1558310@krava> <20200615123048.GB2088119@krava> <8b29e324-eb8d-2266-562b-ca46aec76a3e@linux.intel.com> <20200615165802.GD2088119@krava> <8351b3ee-d345-a394-d687-443f2d2f7ec4@linux.intel.com> <20200622102142.GA2583819@krava> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 22, 2020 at 01:50:03PM +0300, Alexey Budankov wrote: > > On 22.06.2020 13:21, Jiri Olsa wrote: > > On Mon, Jun 22, 2020 at 12:47:19PM +0300, Alexey Budankov wrote: > > > > SNIP > > > >>>>>>>> fdarray__del(array, fdkey); > >>>>>>> > >>>>>>> I think there's solution without having filterable type, > >>>>>>> I'm not sure why you think this is needed > >>>>>>> > >>>>>>> I'm busy with other things this week, but I think I can > >>>>>>> come up with some patch early next week if needed > >>>>>> > >>>>>> Friendly reminder. > >>>>> > >>>>> hm? I believe we discussed this in here: > >>>>> https://lore.kernel.org/lkml/20200609145611.GI1558310@krava/ > >>>> > >>>> Do you want it to be implemented like in the patch posted by the link? > >>> > >>> no idea.. looking for good solution ;-) > >>> > >>> how about switching completely to epoll? I tried and it > >>> does not look that bad > >> > >> Well, epoll() is perhaps possible but why does it want switching to epoll()? > >> What are the benefits and/or specific task being solved by this switch? > > > > epoll change fixes the same issues as the patch you took in v8 > > > > on top of it it's not a hack and wil make polling more user > > friendly because of the clear interface > > Clear. The opposite thing is /proc/sys/fs/epoll/max_user_watches limit that > will affect Perf tool usage additionally to the current process limit on > a number of simultaneously open file descriptors (ulimit -n). So move to > epoll() will impose one limit what can affect Perf tool scalability. hum, I dont think this will be a problem: Allowing top 4% of low memory (per user) to be allocated in epoll watches, we have: LOMEM MAX_WATCHES (per user) 512MB ~178000 1GB ~356000 2GB ~712000 my laptop has 19841945 allowed watches per user > > > > >> > >>> > >>> there might be some loose ends (interface change), but > >>> I think this would solve our problems with fdarray > >> > >> Your first patch accomodated in v8 actually avoids fds typing > >> and solves pos (=fdarray__add()) staleness issue with fdarray. > > > > yea, it was a change meant for discussion (which never happened), > > and I considered it to be more a hack than a solution > > > > I suppose we can live with that for a while, but I'd like to > > have clean solution for polling as well > > I wouldn't treat it as a hack but more as a fix because returned > pos is now a part of interface that can be safely used in callers. > Can we go with this fix for the patch set? apart from this one I still have a problem with that stat factoring having 1 complicated function deal with both fork and no fork processing, which I already commented on, but you ignored ;-) I'll try to go through that once more, and post some comments jirka