linux-kernel - Re: [PATCH] cpuidle: menu: Retain tick when shallow state is selected

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180822120330.GB8949@leoy-ThinkPad-X240s>
Date:   Wed, 22 Aug 2018 20:03:30 +0800
From:   leo.yan@...aro.org
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH] cpuidle: menu: Retain tick when shallow state is selected

On Wed, Aug 22, 2018 at 08:02:00PM +0800, Leo Yan wrote:

[...]

> > +			if (!tick_nohz_tick_stopped()) {
> > +				/*
> > +				 * If the state selected so far is shallow,
> > +				 * waking up early won't hurt, so retain the
> > +				 * tick in that case and let the governor run
> > +				 * again in the next iteration of the loop.
> > +				 */
> > +				expected_interval = drv->states[idx].target_residency;
> > +				break;
> > +			}
> > +
> 
> This is reliable, how we can rely on a shallow idle state target
> residency to decide if need to stop a tick or not?

s/This is reliable/This isn't reliable

> 
> >  			/*
> >  			 * If the state selected so far is shallow and this
> >  			 * state's target residency matches the time till the
> >