Messages in this thread Patch in this message | | | Date | Tue, 23 Aug 2022 13:46:45 -0500 | Subject | Re: [PATCH v3 1/2] ACPI: CPPC: Disable FIE if registers in PCC regions | From | Jeremy Linton <> |
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Hi,
On 8/23/22 12:10, Rafael J. Wysocki wrote: > On Thu, Aug 18, 2022 at 11:24 PM Jeremy Linton <jeremy.linton@arm.com> wrote: >> >> PCC regions utilize a mailbox to set/retrieve register values used by >> the CPPC code. This is fine as long as the operations are >> infrequent. With the FIE code enabled though the overhead can range >> from 2-11% of system CPU overhead (ex: as measured by top) on Arm >> based machines. >> >> So, before enabling FIE assure none of the registers used by >> cppc_get_perf_ctrs() are in the PCC region. Furthermore lets also >> enable a module parameter which can also disable it at boot or module >> reload. >> >> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com> >> --- >> drivers/acpi/cppc_acpi.c | 41 ++++++++++++++++++++++++++++++++++ >> drivers/cpufreq/cppc_cpufreq.c | 31 +++++++++++++++++++++---- >> include/acpi/cppc_acpi.h | 5 +++++ >> 3 files changed, 73 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c >> index 1e15a9f25ae9..c840bf606b30 100644 >> --- a/drivers/acpi/cppc_acpi.c >> +++ b/drivers/acpi/cppc_acpi.c >> @@ -1240,6 +1240,47 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps) >> } >> EXPORT_SYMBOL_GPL(cppc_get_perf_caps); >> >> +/** >> + * cppc_perf_ctrs_in_pcc - Check if any perf counters are in a PCC region. >> + * >> + * CPPC has flexibility about how counters describing CPU perf are delivered. > > "CPU performance counters are accessed"
Sure,
> > >> + * One of the choices is PCC regions, which can have a high access latency. This >> + * routine allows callers of cppc_get_perf_ctrs() to know this ahead of time. >> + * >> + * Return: true if any of the counters are in PCC regions, false otherwise >> + */ >> +bool cppc_perf_ctrs_in_pcc(void) >> +{ >> + int cpu; >> + >> + for_each_present_cpu(cpu) { >> + struct cpc_register_resource *ref_perf_reg; >> + struct cpc_desc *cpc_desc; >> + >> + cpc_desc = per_cpu(cpc_desc_ptr, cpu); >> + >> + if (CPC_IN_PCC(&cpc_desc->cpc_regs[DELIVERED_CTR]) || >> + CPC_IN_PCC(&cpc_desc->cpc_regs[REFERENCE_CTR]) || >> + CPC_IN_PCC(&cpc_desc->cpc_regs[CTR_WRAP_TIME])) >> + return true; >> + >> + >> + ref_perf_reg = &cpc_desc->cpc_regs[REFERENCE_PERF]; >> + >> + /* >> + * If reference perf register is not supported then we should >> + * use the nominal perf value >> + */ >> + if (!CPC_SUPPORTED(ref_perf_reg)) >> + ref_perf_reg = &cpc_desc->cpc_regs[NOMINAL_PERF]; >> + >> + if (CPC_IN_PCC(ref_perf_reg)) >> + return true; >> + } >> + return false; >> +} >> +EXPORT_SYMBOL_GPL(cppc_perf_ctrs_in_pcc); >> + >> /** >> * cppc_get_perf_ctrs - Read a CPU's performance feedback counters. >> * @cpunum: CPU from which to read counters. >> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c >> index 24eaf0ec344d..32fcb0bf74a4 100644 >> --- a/drivers/cpufreq/cppc_cpufreq.c >> +++ b/drivers/cpufreq/cppc_cpufreq.c >> @@ -63,7 +63,15 @@ static struct cppc_workaround_oem_info wa_info[] = { >> >> static struct cpufreq_driver cppc_cpufreq_driver; >> >> +static enum { >> + FIE_UNSET = -1, >> + FIE_ENABLED, >> + FIE_DISABLED >> +} fie_disabled = FIE_UNSET; >> + >> #ifdef CONFIG_ACPI_CPPC_CPUFREQ_FIE >> +module_param(fie_disabled, int, 0444); >> +MODULE_PARM_DESC(fie_disabled, "Disable Frequency Invariance Engine (FIE)"); >> >> /* Frequency invariance support */ >> struct cppc_freq_invariance { >> @@ -158,7 +166,7 @@ static void cppc_cpufreq_cpu_fie_init(struct cpufreq_policy *policy) >> struct cppc_freq_invariance *cppc_fi; >> int cpu, ret; >> >> - if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate) >> + if (fie_disabled) >> return; >> >> for_each_cpu(cpu, policy->cpus) { >> @@ -199,7 +207,7 @@ static void cppc_cpufreq_cpu_fie_exit(struct cpufreq_policy *policy) >> struct cppc_freq_invariance *cppc_fi; >> int cpu; >> >> - if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate) >> + if (fie_disabled) >> return; >> >> /* policy->cpus will be empty here, use related_cpus instead */ >> @@ -229,7 +237,21 @@ static void __init cppc_freq_invariance_init(void) >> }; >> int ret; >> >> - if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate) >> + switch (fie_disabled) { >> + /* honor user request */ >> + case FIE_DISABLED: >> + case FIE_ENABLED: >> + break; >> + case FIE_UNSET: >> + default: > > Would be more straightforward to do > > if (fie_disabled == FIE_UNSET) { > > here.
Right, but then it wouldn't catch the other billion+ values that are the result of not being able to export a limit (AFAIK) on the module parameter. I could use an if:
if !((fie_disabled == FIE_DISABLE) || (fie_disabled == FIE_ENABLED)) {
}
if that is preferable. I thought the case with the explict default: though made it clearer that it was treating all those other values as unset.
> >> + fie_disabled = FIE_ENABLED; >> + if (cppc_perf_ctrs_in_pcc()) { >> + pr_info("FIE not enabled on systems with registers in PCC\n"); >> + fie_disabled = FIE_DISABLED; >> + } >> + break; >> + } >> + if (fie_disabled) >> return; >> >> kworker_fie = kthread_create_worker(0, "cppc_fie"); >> @@ -247,7 +269,7 @@ static void __init cppc_freq_invariance_init(void) >> >> static void cppc_freq_invariance_exit(void) >> { >> - if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate) >> + if (fie_disabled) >> return; >> >> kthread_destroy_worker(kworker_fie); >> @@ -936,6 +958,7 @@ static void cppc_check_hisi_workaround(void) >> wa_info[i].oem_revision == tbl->oem_revision) { >> /* Overwrite the get() callback */ >> cppc_cpufreq_driver.get = hisi_cppc_cpufreq_get_rate; >> + fie_disabled = FIE_DISABLED; >> break; >> } >> } >> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h >> index f73d357ecdf5..c5614444031f 100644 >> --- a/include/acpi/cppc_acpi.h >> +++ b/include/acpi/cppc_acpi.h >> @@ -140,6 +140,7 @@ extern int cppc_get_perf_ctrs(int cpu, struct cppc_perf_fb_ctrs *perf_fb_ctrs); >> extern int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls); >> extern int cppc_set_enable(int cpu, bool enable); >> extern int cppc_get_perf_caps(int cpu, struct cppc_perf_caps *caps); >> +extern bool cppc_perf_ctrs_in_pcc(void); >> extern bool acpi_cpc_valid(void); >> extern bool cppc_allow_fast_switch(void); >> extern int acpi_get_psd_map(unsigned int cpu, struct cppc_cpudata *cpu_data); >> @@ -173,6 +174,10 @@ static inline int cppc_get_perf_caps(int cpu, struct cppc_perf_caps *caps) >> { >> return -ENOTSUPP; >> } >> +static inline bool cppc_perf_ctrs_in_pcc(void) >> +{ >> + return false; >> +} >> static inline bool acpi_cpc_valid(void) >> { >> return false; >> -- > > Apart from the above it looks fine to me, but I would like to get an > ACK from Viresh on the second patch. > > Thanks!
Thanks for looking at this.
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