Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932229Ab3JOMZ3 (ORCPT ); Tue, 15 Oct 2013 08:25:29 -0400 Received: from mail-ee0-f44.google.com ([74.125.83.44]:55067 "EHLO mail-ee0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759127Ab3JOMZ1 (ORCPT ); Tue, 15 Oct 2013 08:25:27 -0400 Date: Tue, 15 Oct 2013 14:25:22 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: Juri Lelli , tglx@linutronix.de, mingo@redhat.com, rostedt@goodmis.org, oleg@redhat.com, fweisbec@gmail.com, darren@dvhart.com, johan.eker@ericsson.com, p.faure@akatech.ch, linux-kernel@vger.kernel.org, claudio@evidence.eu.com, michael@amarulasolutions.com, fchecconi@gmail.com, tommaso.cucinotta@sssup.it, nicola.manica@disi.unitn.it, luca.abeni@unitn.it, dhaval.giani@gmail.com, hgu1972@gmail.com, paulmck@linux.vnet.ibm.com, raistlin@linux.it, insop.song@gmail.com, liming.wang@windriver.com, jkacur@redhat.com, harald.gustafsson@ericsson.com, vincent.guittot@linaro.org, bruce.ashfield@windriver.com--no-chain-reply-to Subject: Re: [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw Message-ID: <20131015122522.GB2402@gmail.com> References: <1381747426-31334-1-git-send-email-juri.lelli@gmail.com> <1381747426-31334-13-git-send-email-juri.lelli@gmail.com> <20131014140618.GA26604@gmail.com> <525D1234.5060001@gmail.com> <20131015102621.GE10651@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131015102621.GE10651@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2126 Lines: 67 * Peter Zijlstra wrote: > On Tue, Oct 15, 2013 at 12:00:20PM +0200, Juri Lelli wrote: > > On 10/14/2013 04:06 PM, Ingo Molnar wrote: > > > > > > * Juri Lelli wrote: > > > > > >> +#ifdef CONFIG_SMP > > >> + struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw; > > >> +#else > > >> + struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw; > > >> +#endif > > > > > >> +#ifdef CONFIG_SMP > > >> + struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw; > > >> +#else > > >> + struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw; > > >> +#endif > > > > > > Btw., this kind of SMP/UP assymetry pattern really sucks. Why not make UP > > > use the SMP data structure, even if it's degenerate? > > > > > > > Yes, I don't like it either, but that comes from the fact that it seemed to me > > that, semantically, bandwidth for -deadline tasks has to be associated to the > > single runqueue in UP and to the root_domain for SMP. In UP root_domain is > > compiled out, so I'm not sure to understand what you suggest. I could probably > > let dl_bw live on runqueues with the assumption that all the runqueues from the > > same root_domain have the same dl_bw, that represents the dl_bw of the > > root_domain. But I don't like this replication either :(. > > #ifdef CONFIG_SMP > > static inline struct dl_bw *dl_bw_of(int i) > { > return &cpu_rq(i)->rd->dl_bw; > } > > #else > > static inline struct dl_bw *dl_bw_of(int i) > { > return &cpu_rq(i)->dl.dl_bw; > } > > #endif > > ? Really, please make it _symmetric_ ... Single core systems are becoming a historic curiosity, should we should justify every piece of extra complexity we add for them. So I'd rather see obvious SMP code where the UP case works fine too, and _then_ maybe check a separate patch that adds the UP optimization, with (object size) numbers proving that it's worth it, etc. Thanks, Ingo -- 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/