Re: [PATCH v3 1/1] x86,sched: On AMD EPYC set freq_max = max_boost in schedutil invariant formula
From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: 2021-02-03 14:12:40
Also in:
linux-pm, lkml
On Wed, Feb 3, 2021 at 2:53 PM Giovanni Gherdovich [off-list ref] wrote:
[cut]
Fixes: 41ea667227ba ("x86, sched: Calculate frequency invariance for AMD systems")
Fixes: 976df7e5730e ("x86, sched: Use midpoint of max_boost and max_P for frequency invariance on AMD EPYC")
Reported-by: Michael Larabel <redacted>
Tested-by: Michael Larabel <redacted>
Signed-off-by: Giovanni Gherdovich <redacted>
---
drivers/cpufreq/acpi-cpufreq.c | 61 ++++++++++++++++++++++++++++++--
drivers/cpufreq/cpufreq.c | 3 ++
include/linux/cpufreq.h | 5 +++
kernel/sched/cpufreq_schedutil.c | 8 +++--I don't really think that it is necessary to modify schedutil to address this issue.
quoted hunk ↗ jump to hunk
4 files changed, 73 insertions(+), 4 deletions(-)diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c index 1e4fbb002a31..a5facc6cad16 100644 --- a/drivers/cpufreq/acpi-cpufreq.c +++ b/drivers/cpufreq/acpi-cpufreq.c@@ -26,6 +26,7 @@ #include <linux/uaccess.h> #include <acpi/processor.h> +#include <acpi/cppc_acpi.h> #include <asm/msr.h> #include <asm/processor.h>@@ -628,11 +629,57 @@ static int acpi_cpufreq_blacklist(struct cpuinfo_x86 *c) } #endif +#ifdef CONFIG_ACPI_CPPC_LIB +static bool amd_max_boost(unsigned int max_freq, + unsigned int *max_boost)
Is there anything specific to AMD CPUs in this function?
+{
+ struct cppc_perf_caps perf_caps;
+ u64 highest_perf, nominal_perf, perf_ratio;
+ int ret;
+
+ ret = cppc_get_perf_caps(0, &perf_caps);
+ if (ret) {
+ pr_debug("Could not retrieve perf counters (%d)\n", ret);
+ return false;
+ }
+
+ highest_perf = perf_caps.highest_perf;
+ nominal_perf = perf_caps.nominal_perf;
+
+ if (!highest_perf || !nominal_perf) {
+ pr_debug("Could not retrieve highest or nominal performance\n");
+ return false;
+ }
+
+ perf_ratio = div_u64(highest_perf * SCHED_CAPACITY_SCALE, nominal_perf);Why do you use SCHED_CAPACITY_SCALE here? And why does this multiply instead of shifting?
+ if (perf_ratio <= SCHED_CAPACITY_SCALE) {
+ pr_debug("Either perf_ratio is 0, or nominal >= highest performance\n");
+ return false;
+ }
+
+ *max_boost = max_freq * perf_ratio >> SCHED_CAPACITY_SHIFT;Is this assuming that max_freq corresponds to nominal_perf?
+ if (!*max_boost) {
+ pr_debug("max_boost seems to be zero\n");
+ return false;So this function may just return the max_boost value with 0 meaning a failure.
quoted hunk ↗ jump to hunk
+ } + + return true; +} +#else +static bool amd_max_boost(unsigned int max_freq, + unsigned int *max_boost) +{ + return false; +} +#endif + static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy) { unsigned int i; unsigned int valid_states = 0; unsigned int cpu = policy->cpu; + unsigned int freq, max_freq = 0; + unsigned int max_boost; struct acpi_cpufreq_data *data; unsigned int result = 0; struct cpuinfo_x86 *c = &cpu_data(policy->cpu);@@ -779,15 +826,25 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy) freq_table[valid_states-1].frequency / 1000) continue; + freq = perf->states[i].core_frequency * 1000; freq_table[valid_states].driver_data = i; - freq_table[valid_states].frequency = - perf->states[i].core_frequency * 1000; + freq_table[valid_states].frequency = freq; + + if (freq > max_freq) + max_freq = freq; + valid_states++; } freq_table[valid_states].frequency = CPUFREQ_TABLE_END; policy->freq_table = freq_table; perf->state = 0; + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD && + amd_max_boost(max_freq, &max_boost)) {
AFAICS, the issue is not limited to AMD CPUs .
quoted hunk ↗ jump to hunk
+ policy->cpuinfo.max_boost = max_boost; + static_branch_enable(&cpufreq_amd_max_boost); + } + switch (perf->control_register.space_id) { case ACPI_ADR_SPACE_SYSTEM_IO: /*diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index d0a3525ce27f..b96677f6b57e 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c@@ -2721,6 +2721,9 @@ int cpufreq_boost_enabled(void) } EXPORT_SYMBOL_GPL(cpufreq_boost_enabled); +DEFINE_STATIC_KEY_FALSE(cpufreq_amd_max_boost); +EXPORT_SYMBOL_GPL(cpufreq_amd_max_boost); + /********************************************************************* * REGISTER / UNREGISTER CPUFREQ DRIVER * *********************************************************************/diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h index 9c8b7437b6cd..341cac76d254 100644 --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h@@ -40,9 +40,14 @@ enum cpufreq_table_sorting { CPUFREQ_TABLE_SORTED_DESCENDING }; +DECLARE_STATIC_KEY_FALSE(cpufreq_amd_max_boost); + +#define cpufreq_driver_has_max_boost() static_branch_unlikely(&cpufreq_amd_max_boost) + struct cpufreq_cpuinfo { unsigned int max_freq; unsigned int min_freq; + unsigned int max_boost; /* in 10^(-9) s = nanoseconds */ unsigned int transition_latency;diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index 6931f0cdeb80..541f3db3f576 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c@@ -159,8 +159,12 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy, unsigned long util, unsigned long max) { struct cpufreq_policy *policy = sg_policy->policy; - unsigned int freq = arch_scale_freq_invariant() ? - policy->cpuinfo.max_freq : policy->cur; + unsigned int freq, max_freq; + + max_freq = cpufreq_driver_has_max_boost() ? + policy->cpuinfo.max_boost : policy->cpuinfo.max_freq; + + freq = arch_scale_freq_invariant() ? max_freq : policy->cur; freq = map_util_freq(util, freq, max); --