From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Rafael Wysocki <rafael.j.wysocki@intel.com>,
Len Brown <len.brown@intel.com>,
Andi Kleen <andi.kleen@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Paul Turner <pjt@google.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Eduardo Valentin <edubezval@gmail.com>,
Punit Agrawal <punit.agrawal@arm.com>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
jacob.jun.pan@linux.intel.com
Subject: Re: [RFC PATCH v2 3/3] sched: introduce synchronized idle injection
Date: Tue, 10 Nov 2015 09:14:08 -0800 [thread overview]
Message-ID: <20151110091408.5e31366c@icelake> (raw)
In-Reply-To: <20151110170010.GH17308@twins.programming.kicks-ass.net>
On Tue, 10 Nov 2015 18:00:10 +0100
Peter Zijlstra <peterz@infradead.org> wrote:
> > Different per CPU timer may intercept parameter changes at slightly
> > different time, so there is a race condition such that some CPUs may
> > catch the period change later by one period, which results in a
> > correct period change but at a different time, i.e. out of sync.
>
> Ah yes. So if the locking hurts I can come up with a lockless
> algorithm for this. Shouldn't be too hard.
Great! the current patch was designed to be lockless but a
little awkward. My idea was to have a common start time, then we don't
need to worry about CPUs out of sync, at most they will be off by one
period then catch up.
Thanks,
Jacob
next prev parent reply other threads:[~2015-11-10 17:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-10 0:21 [RFC PATCH v2 0/3] CFS idle injection Jacob Pan
2015-11-10 0:21 ` [RFC PATCH v2 1/3] ktime: add a roundup function Jacob Pan
2015-11-10 0:21 ` [RFC PATCH v2 2/3] timer: relax tick stop in idle entry Jacob Pan
2015-11-10 0:21 ` [RFC PATCH v2 3/3] sched: introduce synchronized idle injection Jacob Pan
2015-11-10 13:23 ` Peter Zijlstra
2015-11-10 14:01 ` Jacob Pan
2015-11-10 14:58 ` Peter Zijlstra
2015-11-10 16:28 ` Jacob Pan
2015-11-10 16:36 ` Peter Zijlstra
2015-11-10 16:50 ` Jacob Pan
2015-11-10 17:00 ` Peter Zijlstra
2015-11-10 17:14 ` Jacob Pan [this message]
2015-11-10 18:41 ` Jacob Pan
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