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Date: Tue, 18 Feb 2014 13:28:25 +0100 From: Vincent Guittot <vincent.guittot@...aro.org> To: Alex Shi <alex.shi@...aro.org> Cc: Morten Rasmussen <morten.rasmussen@....com>, "mingo@...hat.com" <mingo@...hat.com>, "peterz@...radead.org" <peterz@...radead.org>, "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>, "fweisbec@...il.com" <fweisbec@...il.com>, "linux@....linux.org.uk" <linux@....linux.org.uk>, "tony.luck@...el.com" <tony.luck@...el.com>, "fenghua.yu@...el.com" <fenghua.yu@...el.com>, "james.hogan@...tec.com" <james.hogan@...tec.com>, "jason.low2@...com" <jason.low2@...com>, "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>, "hanjun.guo@...aro.org" <hanjun.guo@...aro.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "tglx@...utronix.de" <tglx@...utronix.de>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "arjan@...ux.intel.com" <arjan@...ux.intel.com>, "pjt@...gle.com" <pjt@...gle.com>, "fengguang.wu@...el.com" <fengguang.wu@...el.com>, "linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>, "wangyun@...ux.vnet.ibm.com" <wangyun@...ux.vnet.ibm.com> Subject: Re: [PATCH v2 0/11] remove cpu_load in rq On 18 February 2014 13:05, Morten Rasmussen <morten.rasmussen@....com> wrote: > On Mon, Feb 17, 2014 at 01:55:06AM +0000, Alex Shi wrote: >> The cpu_load decays on time according past cpu load of rq. The sched_avg also decays tasks' load on time. Now we has 2 kind decay for cpu_load. That is a kind of redundancy. And increase the system load by decay calculation. This patch try to remove the cpu_load decay. >> >> There are 5 load_idx used for cpu_load in sched_domain. busy_idx and idle_idx are not zero usually, but newidle_idx, wake_idx and forkexec_idx are all zero on every arch. A shortcut to remove cpu_Load decay in the first patch. just one line patch for this change. >> >> V2, >> 1, This version do some tuning on load bias of target load, to maximum match current code logical. >> 2, Got further to remove the cpu_load in rq. >> 3, Revert the patch 'Limit sd->*_idx range on sysctl' since no needs >> >> Any testing/comments are appreciated. > > Removing cpu_load completely certainly makes things simpler, my worry is > just how much was lost by doing it. I agree that cpu_load needs a > cleanup, but I can't convince myself that just removing it completely > and not having any longer term view of cpu load anymore is without any > negative side-effects. Hi Alex, Have you followed this thread about load_idx and the interest of using them to use different average period ? https://lkml.org/lkml/2014/1/6/499 Vincent > > {source, target}_load() are now instantaneous views of the cpu load, > which means that they may change very frequently. That could potentially > lead to more task migrations at all levels in the domain hierarchy as we > no longer have the more conservative cpu_load[] indexes that were used > at NUMA level. > > Maybe some of the NUMA experts have an opinion about this? > > In the discussions around V1 I think blocked load came up again as a > potential replacement for the current cpu_load array. There are some > issues that need to be solved around blocked_load first though. > > Morten -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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