Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754374AbbHXVQK (ORCPT ); Mon, 24 Aug 2015 17:16:10 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:36936 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753127AbbHXVQI (ORCPT ); Mon, 24 Aug 2015 17:16:08 -0400 MIME-Version: 1.0 In-Reply-To: <20150824211238.GI28944@mtj.duckdns.org> References: <20150818203117.GC15739@mtj.duckdns.org> <20150822182916.GE20768@mtj.duckdns.org> <55DB3C76.5010009@gmail.com> <20150824170427.GA27262@mtj.duckdns.org> <55DB77F1.5080802@gmail.com> <20150824202509.GF28944@mtj.duckdns.org> <20150824211238.GI28944@mtj.duckdns.org> From: Paul Turner Date: Mon, 24 Aug 2015 14:15:37 -0700 Message-ID: Subject: Re: [PATCH 3/3] sched: Implement interface for cgroup unified hierarchy To: Tejun Heo Cc: Austin S Hemmelgarn , Peter Zijlstra , Ingo Molnar , Johannes Weiner , lizefan@huawei.com, cgroups , LKML , kernel-team , Linus Torvalds , Andrew Morton Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1775 Lines: 38 On Mon, Aug 24, 2015 at 2:12 PM, Tejun Heo wrote: > Hello, Paul. > > On Mon, Aug 24, 2015 at 02:00:54PM -0700, Paul Turner wrote: >> > Hmmm... I'm trying to understand the usecases where having hierarchy >> > inside a process are actually required so that we don't end up doing >> > something complex unnecessarily. So far, it looks like an easy >> > alternative for qemu would be teaching it to manage priorities of its >> > threads given that the threads are mostly static - vcpus going up and >> > down are explicit operations which can trigger priority adjustments if >> > necessary, which is unlikely to begin with. >> >> What you're proposing is both unnecessarily complex and imprecise. >> Arbitrating competition between groups of threads is exactly why we >> support sub-hierarchies within cpu. > > Sure, and to make that behave half-way acceptable, we'll have to take > on significant amount of effort and likely complexity and I'm trying > to see whether the usecases are actually justifiable. I get that > priority based solution will be less precise and more complex on the > application side but by how much and does the added precision enough > to justify the extra facilities to support that? If it is, sure, > let's get to it but it'd be great if the concrete prolem cases are > properly identified and understood. I'll continue on the other reply. > No problem, I think the conversation is absolutely constructive/important to have and am happy to help drill down. > Thanks. > > -- > tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/