From mboxrd@z Thu Jan 1 00:00:00 1970 From: peterz@infradead.org (Peter Zijlstra) Date: Fri, 11 Jul 2014 16:51:38 +0200 Subject: [PATCH v3 08/12] sched: move cfs task on a CPU with higher capacity In-Reply-To: References: <1404144343-18720-1-git-send-email-vincent.guittot@linaro.org> <1404144343-18720-9-git-send-email-vincent.guittot@linaro.org> <20140710111833.GY3935@laptop> Message-ID: <20140711145138.GC3935@laptop> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Jul 10, 2014 at 04:03:51PM +0200, Vincent Guittot wrote: > On 10 July 2014 13:18, Peter Zijlstra wrote: > > On Mon, Jun 30, 2014 at 06:05:39PM +0200, Vincent Guittot wrote: > >> + /* > >> + * If the CPUs share their cache and the src_cpu's capacity is > >> + * reduced because of other sched_class or IRQs, we trig an > >> + * active balance to move the task > >> + */ > >> + if ((sd->flags & SD_SHARE_PKG_RESOURCES) > >> + && ((capacity_orig_of(src_cpu) * 100) > (capacity_of(src_cpu) * > >> + sd->imbalance_pct))) > >> return 1; > > > > Why is this tied to shared caches? > > It's just to limit the change of the policy to a level that can have > benefit without performance regression. I'm not sure that we can do > that at any level without risk Similar to the other change; so both details _should_ have been in the changelogs etc.. In any case, its feels rather arbitrary to me. What about machines where there's no cache sharing at all (the traditional SMP systems). This thing you're trying to do still seems to make sense there.