FIE assumes the delivered/relative perf registers are fast to read so
it goes ahead and hits them quite frequently. On a couple of Arm
platforms though they end up in PCC regions which require mailbox
handshaking with other parts of the platform.
This results in a lot of overhead in the cppc_fie task. As such lets
runtime disable FIE if we detect it enabled on one of those platforms.
Lastly, allow the user to override this decision via a module parameter.
v1->v2:
Apply Rafael's review comments.
Move the MODULE_PARAM into the ifdef
Fix compiler warning when ACPI_CPPC_LIB is disabled.
v2->v3:
Tristate the module param so FIE can be forced on/off
Bump pr_debug to pr_info if FIE is disabled due to PCC regions
Switch ACPI_CPPC_CPUFREQ_FIE off by default
v3->v4:
No functional change, resend due to email addr issues
v4->v5:
Minor whitespace, comment wording, if/case conversion
Drop the ACPI_CPPC_CPUFREQ_FIE disable config change added in v3
Jeremy Linton (1):
ACPI: CPPC: Disable FIE if registers in PCC regions
drivers/acpi/cppc_acpi.c | 42 ++++++++++++++++++++++++++++++++++
drivers/cpufreq/cppc_cpufreq.c | 25 ++++++++++++++++----
include/acpi/cppc_acpi.h | 5 ++++
3 files changed, 68 insertions(+), 4 deletions(-)
--
2.37.1
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. Finally, add a module
parameter which can override the PCC region detection at boot or
module reload.
Signed-off-by: Jeremy Linton <[email protected]>
Acked-by: Viresh Kumar <[email protected]>
---
drivers/acpi/cppc_acpi.c | 42 ++++++++++++++++++++++++++++++++++
drivers/cpufreq/cppc_cpufreq.c | 25 ++++++++++++++++----
include/acpi/cppc_acpi.h | 5 ++++
3 files changed, 68 insertions(+), 4 deletions(-)
diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 1e15a9f25ae9..55693e6f7153 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1240,6 +1240,48 @@ 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 CPU performance counters are accessed.
+ * 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..9e2a48ac5830 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 +237,15 @@ static void __init cppc_freq_invariance_init(void)
};
int ret;
- if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate)
+ if (fie_disabled != FIE_ENABLED && fie_disabled != FIE_DISABLED) {
+ 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;
+ }
+ }
+
+ if (fie_disabled)
return;
kworker_fie = kthread_create_worker(0, "cppc_fie");
@@ -247,7 +263,7 @@ 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 +952,7 @@ 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;
--
2.37.1
Hi Raphael,
Ping, are we good here?
Thanks,
On 9/12/22 15:37, Jeremy Linton 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. Finally, add a module
> parameter which can override the PCC region detection at boot or
> module reload.
>
> Signed-off-by: Jeremy Linton <[email protected]>
> Acked-by: Viresh Kumar <[email protected]>
> ---
> drivers/acpi/cppc_acpi.c | 42 ++++++++++++++++++++++++++++++++++
> drivers/cpufreq/cppc_cpufreq.c | 25 ++++++++++++++++----
> include/acpi/cppc_acpi.h | 5 ++++
> 3 files changed, 68 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index 1e15a9f25ae9..55693e6f7153 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -1240,6 +1240,48 @@ 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 CPU performance counters are accessed.
> + * 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..9e2a48ac5830 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 +237,15 @@ static void __init cppc_freq_invariance_init(void)
> };
> int ret;
>
> - if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate)
> + if (fie_disabled != FIE_ENABLED && fie_disabled != FIE_DISABLED) {
> + 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;
> + }
> + }
> +
> + if (fie_disabled)
> return;
>
> kworker_fie = kthread_create_worker(0, "cppc_fie");
> @@ -247,7 +263,7 @@ 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 +952,7 @@ 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;
Hi Jeremy,
On Monday 12 Sep 2022 at 15:37:22 (-0500), Jeremy Linton 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. Finally, add a module
> parameter which can override the PCC region detection at boot or
> module reload.
>
> Signed-off-by: Jeremy Linton <[email protected]>
> Acked-by: Viresh Kumar <[email protected]>
> ---
> drivers/acpi/cppc_acpi.c | 42 ++++++++++++++++++++++++++++++++++
> drivers/cpufreq/cppc_cpufreq.c | 25 ++++++++++++++++----
> include/acpi/cppc_acpi.h | 5 ++++
> 3 files changed, 68 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index 1e15a9f25ae9..55693e6f7153 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -1240,6 +1240,48 @@ 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 CPU performance counters are accessed.
> + * 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..9e2a48ac5830 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);
Why 'int' and not 'bool' here?
IIUC, if you use 'bool' the user can pass any int/0/1/y/n/Y/N, which
will result in fie_disabled properly having either the value 0 or 1
(or default FIE_UNSET) if a parameter is not passed.
Then
'if (fie_disabled != FIE_ENABLED && fie_disabled != FIE_DISABLED)'
can become
'if (fie_disabled == FIE_UNSET)' or 'if (fie_disabled < 0)'.
I feel I'm missing something, otherwise you would have done this
already.
Otherwise FWIW, it looks good to me.
Reviewed-by: Ionela Voinescu <[email protected]>
Thanks,
Ionela.
> +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 +237,15 @@ static void __init cppc_freq_invariance_init(void)
> };
> int ret;
>
> - if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate)
> + if (fie_disabled != FIE_ENABLED && fie_disabled != FIE_DISABLED) {
> + 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;
> + }
> + }
> +
> + if (fie_disabled)
> return;
>
> kworker_fie = kthread_create_worker(0, "cppc_fie");
> @@ -247,7 +263,7 @@ 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 +952,7 @@ 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;
> --
> 2.37.1
>
On Fri, Sep 23, 2022 at 6:31 PM Ionela Voinescu <[email protected]> wrote:
>
> Hi Jeremy,
>
> On Monday 12 Sep 2022 at 15:37:22 (-0500), Jeremy Linton 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. Finally, add a module
> > parameter which can override the PCC region detection at boot or
> > module reload.
> >
> > Signed-off-by: Jeremy Linton <[email protected]>
> > Acked-by: Viresh Kumar <[email protected]>
> > ---
> > drivers/acpi/cppc_acpi.c | 42 ++++++++++++++++++++++++++++++++++
> > drivers/cpufreq/cppc_cpufreq.c | 25 ++++++++++++++++----
> > include/acpi/cppc_acpi.h | 5 ++++
> > 3 files changed, 68 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> > index 1e15a9f25ae9..55693e6f7153 100644
> > --- a/drivers/acpi/cppc_acpi.c
> > +++ b/drivers/acpi/cppc_acpi.c
> > @@ -1240,6 +1240,48 @@ 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 CPU performance counters are accessed.
> > + * 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..9e2a48ac5830 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);
>
> Why 'int' and not 'bool' here?
>
> IIUC, if you use 'bool' the user can pass any int/0/1/y/n/Y/N, which
> will result in fie_disabled properly having either the value 0 or 1
> (or default FIE_UNSET) if a parameter is not passed.
>
> Then
> 'if (fie_disabled != FIE_ENABLED && fie_disabled != FIE_DISABLED)'
> can become
> 'if (fie_disabled == FIE_UNSET)' or 'if (fie_disabled < 0)'.
>
> I feel I'm missing something, otherwise you would have done this
> already.
>
> Otherwise FWIW, it looks good to me.
> Reviewed-by: Ionela Voinescu <[email protected]>
Applied as 6.1 material, thanks!
> > +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 +237,15 @@ static void __init cppc_freq_invariance_init(void)
> > };
> > int ret;
> >
> > - if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate)
> > + if (fie_disabled != FIE_ENABLED && fie_disabled != FIE_DISABLED) {
> > + 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;
> > + }
> > + }
> > +
> > + if (fie_disabled)
> > return;
> >
> > kworker_fie = kthread_create_worker(0, "cppc_fie");
> > @@ -247,7 +263,7 @@ 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 +952,7 @@ 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;
> > --
> > 2.37.1
> >