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From: Ionela Voinescu <ionela.voinescu@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com,
	maz@kernel.org, suzuki.poulose@arm.com, sudeep.holla@arm.com,
	dietmar.eggemann@arm.com, mingo@redhat.com, ggherdovich@suse.cz,
	vincent.guittot@linaro.org, linux-arm-kernel@lists.infradead.org,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	Juri Lelli <juri.lelli@redhat.com>
Subject: Re: [PATCH v2 5/6] TEMP: sched: add interface for counter-based frequency invariance
Date: Thu, 30 Jan 2020 15:33:25 +0000	[thread overview]
Message-ID: <20200130153325.GA5208@arm.com> (raw)
In-Reply-To: <20200129193741.GU14914@hirez.programming.kicks-ass.net>

On Wednesday 29 Jan 2020 at 20:37:41 (+0100), Peter Zijlstra wrote:
> On Wed, Dec 18, 2019 at 06:26:06PM +0000, Ionela Voinescu wrote:
> > To be noted that this patch is a temporary one. It introduces the
> > interface added by the patches at [1] to allow update of the frequency
> > invariance scale factor based on counters. If [1] is merged there is
> > not need for this patch.
> > 
> > For platforms that support counters (x86 - APERF/MPERF, arm64 - AMU
> > counters) the frequency invariance correction factor can be obtained
> > using a core counter and a fixed counter to get information on the
> > performance (frequency based only) obtained in a period of time. This
> > will more accurately reflect the actual current frequency of the CPU,
> > compared with the alternative implementation that reflects the request
> > of a performance level from the OS through the cpufreq framework
> > (arch_set_freq_scale).
> > 
> > Therefore, introduce an interface - arch_scale_freq_tick, to be
> > implemented by each architecture and called for each CPU on the tick
> > to update the scale factor based on the delta in the counter values,
> > if counter support is present on the CPU.
> > 
> > Either because reading counters is expensive or because reading
> > counters from remote CPUs is not possible or is expensive, only
> > update the counter based frequency scale factor on the tick for
> > now. A tick based update will definitely be necessary either due to
> > it being the only point of update for certain architectures or in
> > order to cache the counter values for a particular CPU, if a
> > further update from that CPU is not possible.
> > 
> > [1]
> > https://lore.kernel.org/lkml/20191113124654.18122-1-ggherdovich@suse.cz/
> 
> FWIW, those patches just landed in tip/sched/core

Thanks, Peter, I'll drop this one next time around.

Ionela.

  reply	other threads:[~2020-01-30 15:33 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-18 18:26 [PATCH v2 0/6] arm64: ARMv8.4 Activity Monitors support Ionela Voinescu
2019-12-18 18:26 ` [PATCH v2 1/6] arm64: add support for the AMU extension v1 Ionela Voinescu
2020-01-23 17:04   ` Valentin Schneider
2020-01-23 18:32     ` Ionela Voinescu
2020-01-24 12:00       ` Valentin Schneider
2020-01-28 11:00         ` Ionela Voinescu
2020-01-28 16:34   ` Suzuki Kuruppassery Poulose
2020-01-29 16:42     ` Ionela Voinescu
2019-12-18 18:26 ` [PATCH v2 2/6] arm64: trap to EL1 accesses to AMU counters from EL0 Ionela Voinescu
2020-01-23 17:04   ` Valentin Schneider
2020-01-23 17:34     ` Ionela Voinescu
2019-12-18 18:26 ` [PATCH v2 3/6] arm64/kvm: disable access to AMU registers from kvm guests Ionela Voinescu
2020-01-27 15:33   ` Valentin Schneider
2020-01-28 15:48     ` Ionela Voinescu
2020-01-28 17:26     ` Suzuki Kuruppassery Poulose
2020-01-28 17:37       ` Valentin Schneider
2020-01-28 17:52         ` Ionela Voinescu
2019-12-18 18:26 ` [PATCH v2 4/6] Documentation: arm64: document support for the AMU extension Ionela Voinescu
2020-01-27 16:47   ` Valentin Schneider
2020-01-28 16:53     ` Ionela Voinescu
2020-01-28 18:36       ` Valentin Schneider
2020-01-30 15:04   ` Suzuki Kuruppassery Poulose
2020-01-30 16:45     ` Ionela Voinescu
2020-01-30 18:26       ` Suzuki K Poulose
2020-01-31  9:54         ` Ionela Voinescu
2019-12-18 18:26 ` [PATCH v2 5/6] TEMP: sched: add interface for counter-based frequency invariance Ionela Voinescu
2020-01-29 19:37   ` Peter Zijlstra
2020-01-30 15:33     ` Ionela Voinescu [this message]
2019-12-18 18:26 ` [PATCH v2 6/6] arm64: use activity monitors for " Ionela Voinescu
2020-01-23 11:49   ` Lukasz Luba
2020-01-23 17:07     ` Ionela Voinescu
2020-01-24  1:19       ` Lukasz Luba
2020-01-24 13:12         ` Ionela Voinescu
2020-01-24 15:17           ` Lukasz Luba
2020-01-28 17:36             ` Ionela Voinescu
2020-01-29 17:13   ` Valentin Schneider
2020-01-29 17:52     ` Ionela Voinescu
2020-01-29 23:39     ` Valentin Schneider
2020-01-30 15:49       ` Ionela Voinescu
2020-01-30 16:11         ` Valentin Schneider

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