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Message-ID: <7f869bc1-9129-48b2-b0fd-483c790a8d1b@zhaoxin.com>
Date: Wed, 31 Jan 2024 18:55:25 +0800
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Subject: Re: [PATCH 3/3] ACPI: cpufreq: Add ITMT support when CPPC enabled for
 Zhaoxin CPUs
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To: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
CC: <rafael@kernel.org>, <lenb@kernel.org>, <robert.moore@intel.com>,
	<linux-acpi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<acpica-devel@lists.linux.dev>, <tglx@linutronix.de>, <mingo@redhat.com>,
	<bp@alien8.de>, <dave.hansen@linux.intel.com>, <x86@kernel.org>,
	<hpa@zytor.com>, <mcgrof@kernel.org>, <peterz@infradead.org>,
	<j.granados@samsung.com>, <viresh.kumar@linaro.org>,
	<linux-pm@vger.kernel.org>, <CobeChen@zhaoxin.com>, <TimGuo@zhaoxin.com>,
	<LeoLiu-oc@zhaoxin.com>, <LindaChai@zhaoxin.com>
References: <20231228075705.26652-1-TonyWWang-oc@zhaoxin.com>
 <20231228075705.26652-4-TonyWWang-oc@zhaoxin.com>
 <20240117225158.GD13777@ranerica-svr.sc.intel.com>
From: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
In-Reply-To: <20240117225158.GD13777@ranerica-svr.sc.intel.com>
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On 2024/1/18 06:51, Ricardo Neri wrote:
>
> [这封邮件来自外部发件人]
>
> On Thu, Dec 28, 2023 at 03:57:05PM +0800, Tony W Wang-oc wrote:
>> For Zhaoxin CPUs, the cores' highest frequencies may be different, which
>> means that cores may run at different max frequencies,
>>
>> According to ACPI-spec6 chapter 8.4.7, the per-core highest frequency
>> value can be obtained via cppc.
>>
>> The core with the higher frequency have better performance, which can be
>> called as preferred core. And better performance can be achieved by
>> making the scheduler to run tasks on these preferred cores.
>>
>> The cpufreq driver can use the highest frequency value as the prioriy of
>> core to make the scheduler try to get better performace. More specifically,
>> in the acpi-cpufreq driver use cppc_get_highest_perf() to get highest
>> frequency value of each core, use sched_set_itmt_core_prio() to set
>> highest frequency value as core priority, and use sched_set_itmt_support()
>> provided by ITMT to tell the scheduler to favor on the preferred cores.
>>
>> Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
>> ---
>>   drivers/cpufreq/acpi-cpufreq.c | 56 +++++++++++++++++++++++++++++++++-
>>   1 file changed, 55 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
>> index 37f1cdf46d29..f4c1ff9e4bb0 100644
>> --- a/drivers/cpufreq/acpi-cpufreq.c
>> +++ b/drivers/cpufreq/acpi-cpufreq.c
>> @@ -663,8 +663,56 @@ static u64 get_max_boost_ratio(unsigned int cpu)
>>
>>        return div_u64(highest_perf << SCHED_CAPACITY_SHIFT, nominal_perf);
>>   }
>> +
>> +/* The work item is needed to avoid CPU hotplug locking issues */
>> +static void sched_itmt_work_fn(struct work_struct *work)
>> +{
>> +     sched_set_itmt_support();
>> +}
>> +
>> +static DECLARE_WORK(sched_itmt_work, sched_itmt_work_fn);
>> +
>> +static void set_itmt_prio(int cpu)
>> +{
>> +     static bool cppc_highest_perf_diff;
>> +     static struct cpumask core_prior_mask;
>> +     u64 highest_perf;
>> +     static u64 max_highest_perf = 0, min_highest_perf = U64_MAX;
>> +     int ret;
>> +
>> +     ret = cppc_get_highest_perf(cpu, &highest_perf);
>> +     if (ret)
>> +             return;
>> +
>> +     sched_set_itmt_core_prio(highest_perf, cpu);
>> +     cpumask_set_cpu(cpu, &core_prior_mask);
>> +
>> +     if (max_highest_perf <= min_highest_perf) {
>> +             if (highest_perf > max_highest_perf)
>> +                     max_highest_perf = highest_perf;
>> +
>> +             if (highest_perf < min_highest_perf)
>> +                     min_highest_perf = highest_perf;
>> +
>> +             if (max_highest_perf > min_highest_perf) {
>> +                     /*
>> +                      * This code can be run during CPU online under the
>> +                      * CPU hotplug locks, so sched_set_itmt_support()
>> +                      * cannot be called from here.  Queue up a work item
>> +                      * to invoke it.
>> +                      */
>> +                     cppc_highest_perf_diff = true;
>> +             }
>> +     }
>> +
>> +     if (cppc_highest_perf_diff && cpumask_equal(&core_prior_mask, cpu_online_mask)) {
>> +             pr_debug("queue a work to set itmt enabled\n");
>> +             schedule_work(&sched_itmt_work);
>> +     }
>> +}
> sched_itmt_work and this function is a duplicate of what the intel_pstate
> driver already does. It might be good if consolidate in a single place
> if you are going to pursue this approach.

Thanks for your suggestion, will change the patch code in v2.

Sorry for late.