Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754338AbaKXOlw (ORCPT ); Mon, 24 Nov 2014 09:41:52 -0500 Received: from mail-oi0-f41.google.com ([209.85.218.41]:50440 "EHLO mail-oi0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752909AbaKXOlt (ORCPT ); Mon, 24 Nov 2014 09:41:49 -0500 MIME-Version: 1.0 In-Reply-To: <20141121123719.GH23177@e105550-lin.cambridge.arm.com> References: <1415033687-23294-1-git-send-email-vincent.guittot@linaro.org> <1415033687-23294-9-git-send-email-vincent.guittot@linaro.org> <20141121123719.GH23177@e105550-lin.cambridge.arm.com> From: Vincent Guittot Date: Mon, 24 Nov 2014 15:41:28 +0100 Message-ID: Subject: Re: [PATCH v9 08/10] sched: replace capacity_factor by usage To: Morten Rasmussen Cc: "peterz@infradead.org" , "mingo@kernel.org" , "linux-kernel@vger.kernel.org" , "preeti@linux.vnet.ibm.com" , "kamalesh@linux.vnet.ibm.com" , "linux-arm-kernel@lists.infradead.org" , "riel@redhat.com" , "efault@gmx.de" , "nicolas.pitre@linaro.org" , "linaro-kernel@lists.linaro.org" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21 November 2014 at 13:37, Morten Rasmussen wrote: > On Mon, Nov 03, 2014 at 04:54:45PM +0000, Vincent Guittot wrote: [snip] >> */ >> if (prefer_sibling && sds->local && >> - sds->local_stat.group_has_free_capacity) >> - sgs->group_capacity_factor = min(sgs->group_capacity_factor, 1U); >> + group_has_capacity(env, &sds->local_stat) && >> + (sgs->sum_nr_running > 1)) { >> + sgs->group_no_capacity = 1; >> + sgs->group_type = group_overloaded; >> + } > > I'm still a bit confused about SD_PREFER_SIBLING. What is the flag > supposed to do and why? The goal is to spread tasks across the group even if the the latter is not overloaded. for SMT level, the goal is to have 1 task per core before 1 task per HW thread > > It looks like a weak load balancing bias attempting to consolidate tasks > on domains with spare capacity. It does so by marking non-local groups > as overloaded regardless of their actual load if the local group has > spare capacity. Correct? > > In patch 9 this behaviour is enabled for SMT level domains, which > implies that tasks will be consolidated in MC groups, that is we prefer > multiple tasks on sibling cpus (hw threads). I must be missing something > essential. I was convinced that we wanted to avoid using sibling cpus on > SMT systems as much as possible? > > -- > 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/ -- 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/