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Date: Fri, 22 Mar 2019 14:26:07 +0100 From: Daniel Lezcano <daniel.lezcano@...aro.org> To: "Rafael J. Wysocki" <rafael@...nel.org>, Abhishek Goel <huntbag@...ux.vnet.ibm.com> Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>, Linux PM <linux-pm@...r.kernel.org>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Michael Ellerman <mpe@...erman.id.au> Subject: Re: [PATCH 1/2] cpuidle : auto-promotion for cpuidle states On 22/03/2019 10:45, Rafael J. Wysocki wrote: > On Fri, Mar 22, 2019 at 8:31 AM Abhishek Goel > <huntbag@...ux.vnet.ibm.com> wrote: >> >> Currently, the cpuidle governors (menu /ladder) determine what idle state >> an idling CPU should enter into based on heuristics that depend on the >> idle history on that CPU. Given that no predictive heuristic is perfect, >> there are cases where the governor predicts a shallow idle state, hoping >> that the CPU will be busy soon. However, if no new workload is scheduled >> on that CPU in the near future, the CPU will end up in the shallow state. >> >> In case of POWER, this is problematic, when the predicted state in the >> aforementioned scenario is a lite stop state, as such lite states will >> inhibit SMT folding, thereby depriving the other threads in the core from >> using the core resources. >> >> To address this, such lite states need to be autopromoted. The cpuidle- >> core can queue timer to correspond with the residency value of the next >> available state. Thus leading to auto-promotion to a deeper idle state as >> soon as possible. > > Isn't the tick stopping avoidance sufficient for that? I was about to ask the same :) -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
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