From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754958AbeDZJ0w (ORCPT ); Thu, 26 Apr 2018 05:26:52 -0400 Received: from mail-eopbgr00100.outbound.protection.outlook.com ([40.107.0.100]:52356 "EHLO EUR02-AM5-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754934AbeDZJ0p (ORCPT ); Thu, 26 Apr 2018 05:26:45 -0400 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=ktkhai@virtuozzo.com; Subject: Re: [PATCH] sched/rt: Rework for_each_process_thread() iterations in tg_has_rt_tasks() To: Peter Zijlstra Cc: mingo@redhat.com, linux-kernel@vger.kernel.org, Juri Lelli References: <152415882713.2054.8734093066910722403.stgit@localhost.localdomain> <20180425175535.GC4043@hirez.programming.kicks-ass.net> From: Kirill Tkhai Message-ID: Date: Thu, 26 Apr 2018 12:26:36 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180425175535.GC4043@hirez.programming.kicks-ass.net> Content-Type: text/plain; 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I myself don't use them, but this goes from CRIU project. We try to dump and to restore every configuration that people may use. Sometimes they configure RT parameters of cpu cgroup, and criu has to restore them as they was at the moment of dump. So, this is the place, where we met the hard lockup. I can't say, what forces people to use nested cpu cgroup for RT... > Some of us recently considered removing that thing entirely because most > distro's don't actually use it at all -- and it's broken from a RT POV. > > That would then clear the slate to try and implement something new. > > But if you're actually using this stuff, that would complicate matters. >>From the point of criu project, if you delete them, this will decrease the number of essence we need to support, so I'm not against that :D Seriously speaking, it's a surprise for me, that they are broken. It seemed, everything is nice from RT POV: throttling, boosting, PI... Kirill