From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
x86 Maintainers <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux PM <linux-pm@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Ricardo Neri <ricardo.neri@intel.com>,
Tim Chen <tim.c.chen@intel.com>
Subject: Re: [RFC][PATCH v1 3/3] cpufreq: intel_pstate: Set asymmetric CPU capacity on hybrid systems
Date: Fri, 3 May 2024 20:29:51 +0200 [thread overview]
Message-ID: <0b849052-0eb1-4085-aa65-73b7451cd6ba@arm.com> (raw)
In-Reply-To: <20240503033242.GA14835@ranerica-svr.sc.intel.com>
On 03/05/2024 05:32, Ricardo Neri wrote:
> On Thu, May 02, 2024 at 12:42:54PM +0200, Dietmar Eggemann wrote:
>> On 25/04/2024 21:06, Rafael J. Wysocki wrote:
>>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>>
>>> Make intel_pstate use the HWP_HIGHEST_PERF values from
>>> MSR_HWP_CAPABILITIES to set asymmetric CPU capacity information
>>> via the previously introduced arch_set_cpu_capacity() on hybrid
>>> systems without SMT.
>>
>> Are there such systems around? My i7-13700K has P-cores (CPU0..CPU15)
>> with SMT.
>
> We have been experimenting with nosmt in the kernel command line.
OK.
[...]
>>> If the given system is hybrid and non-SMT, the new code disables ITMT
>>> support in the scheduler (because it may get in the way of asymmetric CPU
>>> capacity code in the scheduler that automatically gets enabled by setting
>>> asymmetric CPU capacity) after initializing all online CPUs and finds
>>> the one with the maximum HWP_HIGHEST_PERF value. Next, it computes the
>>> capacity number for each (online) CPU by dividing the product of its
>>> HWP_HIGHEST_PERF and SCHED_CAPACITY_SCALE by the maximum HWP_HIGHEST_PERF.
>>
>> SO either CAS at wakeup and in load_balance or SIS at wakeup and ITMT in
>> load balance.
>
> May I know what CAS and SIS stand for?
Capacity Aware Scheduling and Select_Idle_Sibling().
Either select_idle_sibling() -> select_idle_capacity() (1)
or select_idle_sibling() -> select_idle_cpu() /* nosmt */ (2)
So my system with now 'nosmt' goes (1).
next prev parent reply other threads:[~2024-05-03 18:30 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-25 19:03 [RFC][PATCH v1 0/3] x86 / intel_pstate: Set asymmetric CPU capacity on hybrid systems Rafael J. Wysocki
2024-04-25 19:04 ` [RFC][PATCH v1 1/3] x86/sched: Introduce arch_rebuild_sched_domains() Rafael J. Wysocki
2024-04-25 19:04 ` [RFC][PATCH v1 2/3] " Rafael J. Wysocki
2024-04-25 19:14 ` Rafael J. Wysocki
2024-04-25 19:15 ` [RFC][PATCH v1 2/3] x86/sched: Add basic support for CPU capacity scaling Rafael J. Wysocki
2024-04-25 19:06 ` [RFC][PATCH v1 3/3] cpufreq: intel_pstate: Set asymmetric CPU capacity on hybrid systems Rafael J. Wysocki
2024-05-02 10:42 ` Dietmar Eggemann
2024-05-03 3:32 ` Ricardo Neri
2024-05-03 18:29 ` Dietmar Eggemann [this message]
2024-05-06 14:39 ` Rafael J. Wysocki
2024-05-21 12:51 ` Dietmar Eggemann
2024-05-24 12:43 ` Dietmar Eggemann
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