From: Ionela Voinescu <ionela.voinescu@arm.com>
To: Thara Gopinath <thara.gopinath@linaro.org>
Cc: mingo@redhat.com, peterz@infradead.org,
vincent.guittot@linaro.org, rui.zhang@intel.com,
qperret@google.com, daniel.lezcano@linaro.org,
viresh.kumar@linaro.org, linux-kernel@vger.kernel.org,
amit.kachhap@gmail.com, javi.merino@kernel.org,
amit.kucheria@verdurent.com
Subject: Re: [Patch v6 3/7] Add infrastructure to store and update instantaneous thermal pressure
Date: Mon, 23 Dec 2019 17:50:20 +0000 [thread overview]
Message-ID: <20191223175005.GA31446@arm.com> (raw)
In-Reply-To: <1576123908-12105-4-git-send-email-thara.gopinath@linaro.org>
Hi Thara,
On Wednesday 11 Dec 2019 at 23:11:44 (-0500), Thara Gopinath wrote:
> Add architecture specific APIs to update and track thermal pressure on a
> per cpu basis. A per cpu variable thermal_pressure is introduced to keep
> track of instantaneous per cpu thermal pressure. Thermal pressure is the
> delta between maximum capacity and capped capacity due to a thermal event.
> capacity and capped capacity due to a thermal event.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This line seems to be a duplicate (initially I thought I was seeing
double :) ).
> topology_get_thermal_pressure can be hooked into the scheduler specified
> arch_scale_thermal_capacity to retrieve instantaneius thermal pressure of
> a cpu.
>
> arch_set_thermal_presure can be used to update the thermal pressure by
> providing a capped maximum capacity.
>
> Considering topology_get_thermal_pressure reads thermal_pressure and
> arch_set_thermal_pressure writes into thermal_pressure, one can argue for
> some sort of locking mechanism to avoid a stale value. But considering
> topology_get_thermal_pressure_average can be called from a system critical
> path like scheduler tick function, a locking mechanism is not ideal. This
> means that it is possible the thermal_pressure value used to calculate
> average thermal pressure for a cpu can be stale for upto 1 tick period.
>
> Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
[...]
> diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h
> index 8a0fae9..90b18c3 100644
> --- a/arch/arm/include/asm/topology.h
> +++ b/arch/arm/include/asm/topology.h
> @@ -16,6 +16,9 @@
> /* Enable topology flag updates */
> #define arch_update_cpu_topology topology_update_cpu_topology
>
> +/* Replace task scheduler's defalut thermal pressure retrieve API */
s/defalut/default
> +#define arch_scale_thermal_capacity topology_get_thermal_pressure
> +
I also think this is deserving of a better name. I would drop the
'scale' part as well as it is not used as a scale factor, as
freq_scale or cpu_scale, but it's used as a reduction in capacity
(thermal capacity pressure) due to a thermal event.
It might be too much but what do you think about:
arch_thermal_capacity_pressure?
> #else
>
> static inline void init_cpu_topology(void) { }
> diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
> index a4d945d..ccb277b 100644
> --- a/arch/arm64/include/asm/topology.h
> +++ b/arch/arm64/include/asm/topology.h
> @@ -25,6 +25,9 @@ int pcibus_to_node(struct pci_bus *bus);
> /* Enable topology flag updates */
> #define arch_update_cpu_topology topology_update_cpu_topology
>
> +/* Replace task scheduler's defalut thermal pressure retrieve API */
s/defalut/default
Regards,
Ionela.
next prev parent reply other threads:[~2019-12-23 17:50 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-12 4:11 [Patch v6 0/7] Introduce Thermal Pressure Thara Gopinath
2019-12-12 4:11 ` [Patch v6 1/7] sched/pelt.c: Add support to track thermal pressure Thara Gopinath
2019-12-16 13:43 ` Peter Zijlstra
2019-12-17 12:54 ` Dietmar Eggemann
[not found] ` <CALD-y_xHS7CaZ8SU--VP5+2F5Y8cVb4sw0XuG+JUpP_jxE7yuQ@mail.gmail.com>
2020-01-09 12:24 ` Dietmar Eggemann
2019-12-23 17:56 ` Ionela Voinescu
2020-01-02 14:40 ` Thara Gopinath
2019-12-12 4:11 ` [Patch v6 2/7] sched: Add hook to read per cpu " Thara Gopinath
2019-12-16 14:35 ` Peter Zijlstra
2019-12-17 12:54 ` Dietmar Eggemann
2019-12-12 4:11 ` [Patch v6 3/7] Add infrastructure to store and update instantaneous " Thara Gopinath
2019-12-16 14:37 ` Peter Zijlstra
2019-12-17 12:54 ` Dietmar Eggemann
2019-12-23 17:50 ` Ionela Voinescu [this message]
2019-12-12 4:11 ` [Patch v6 4/7] sched/fair: Enable periodic update of average " Thara Gopinath
2019-12-16 14:39 ` Peter Zijlstra
2019-12-16 17:59 ` Quentin Perret
2019-12-17 12:57 ` Dietmar Eggemann
2019-12-27 15:22 ` Thara Gopinath
2019-12-12 4:11 ` [Patch v6 5/7] sched/fair: update cpu_capacity to reflect " Thara Gopinath
2019-12-17 12:54 ` Dietmar Eggemann
2019-12-23 17:52 ` Ionela Voinescu
2019-12-12 4:11 ` [Patch v6 6/7] thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping Thara Gopinath
2019-12-23 17:54 ` Ionela Voinescu
2019-12-12 4:11 ` [Patch v6 7/7] sched/fair: Enable tuning of decay period Thara Gopinath
2019-12-23 17:55 ` Ionela Voinescu
2019-12-16 14:56 ` [Patch v6 0/7] Introduce Thermal Pressure Peter Zijlstra
2020-01-11 15:04 ` Thara Gopinath
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