[PATCH v2 2/2] powercap/rapl: reduce ipi calls

Jacob Pan
2016-01-13T01:11:23Z

Reduce remote CPU calls for MSR access by combining read
modify write into one function. Also optimize search for active CPU on
package.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
drivers/powercap/intel_rapl.c | 77 +++++++++++++++++++++++--------------------
1 file changed, 42 insertions(+), 35 deletions(-)

diff --git a/drivers/powercap/intel_rapl.c b/drivers/powercap/intel_rapl.c
index 48747c2..b34d6a6 100644
--- a/drivers/powercap/intel_rapl.c
+++ b/drivers/powercap/intel_rapl.c
@@ -263,7 +263,11 @@ static struct rapl_package *find_package_by_id(int id)
/* caller to ensure CPU hotplug lock is held */
static int find_active_cpu_on_package(int package_id)
{
- int i;
+ /* try to avoid remote cpu call, use raw since we are preemptible */
+ int i = raw_smp_processor_id();
+
+ if (topology_physical_package_id(i) == package_id)
+ return i;

for_each_online_cpu(i) {
if (topology_physical_package_id(i) == package_id)
@@ -805,30 +809,18 @@ static int rapl_write_data_raw(struct rapl_domain *rd,
enum rapl_primitives prim,
unsigned long long value)
{
- u64 msr_val;
- u32 msr;
struct rapl_primitive_info *rp = &rpi[prim];
int cpu;
+ u64 bits;

cpu = find_active_cpu_on_package(rd->package_id);
if (cpu < 0)
return cpu;
- msr = rd->msrs[rp->id];
- if (rdmsrl_safe_on_cpu(cpu, msr, &msr_val)) {
- dev_dbg(&rd->power_zone.dev,
- "failed to read msr 0x%x on cpu %d\n", msr, cpu);
- return -EIO;
- }
- value = rapl_unit_xlate(rd, rd->package_id, rp->unit, value, 1);
- msr_val &= ~rp->mask;
- msr_val |= value << rp->shift;
- if (wrmsrl_safe_on_cpu(cpu, msr, msr_val)) {
- dev_dbg(&rd->power_zone.dev,
- "failed to write msr 0x%x on cpu %d\n", msr, cpu);
- return -EIO;
- }

- return 0;
+ bits = rapl_unit_xlate(rd, rd->package_id, rp->unit, value, 1);
+ bits |= bits << rp->shift;
+
+ return rmwmsrl_safe_on_cpu(cpu, rd->msrs[rp->id], rp->mask, bits);
}

/*
@@ -893,6 +885,21 @@ static int rapl_check_unit_atom(struct rapl_package *rp, int cpu)
return 0;
}

+static void power_limit_irq_save_cpu(void *info)
+{
+ u32 l, h = 0;
+ struct rapl_package *rp = (struct rapl_package *)info;
+
+ /* save the state of PLN irq mask bit before disabling it */
+ rdmsr_safe(MSR_IA32_PACKAGE_THERM_INTERRUPT, &l, &h);
+ if (!(rp->power_limit_irq & PACKAGE_PLN_INT_SAVED)) {
+ rp->power_limit_irq = l & PACKAGE_THERM_INT_PLN_ENABLE;
+ rp->power_limit_irq |= PACKAGE_PLN_INT_SAVED;
+ }
+ l &= ~PACKAGE_THERM_INT_PLN_ENABLE;
+ wrmsr_safe(MSR_IA32_PACKAGE_THERM_INTERRUPT, l, h);
+}
+

/* REVISIT:
* When package power limit is set artificially low by RAPL, LVT
@@ -906,7 +913,6 @@ static int rapl_check_unit_atom(struct rapl_package *rp, int cpu)

static void package_power_limit_irq_save(int package_id)
{
- u32 l, h = 0;
int cpu;
struct rapl_package *rp;

@@ -920,20 +926,27 @@ static void package_power_limit_irq_save(int package_id)
cpu = find_active_cpu_on_package(package_id);
if (cpu < 0)
return;
- /* save the state of PLN irq mask bit before disabling it */
- rdmsr_safe_on_cpu(cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT, &l, &h);
- if (!(rp->power_limit_irq & PACKAGE_PLN_INT_SAVED)) {
- rp->power_limit_irq = l & PACKAGE_THERM_INT_PLN_ENABLE;
- rp->power_limit_irq |= PACKAGE_PLN_INT_SAVED;
- }
- l &= ~PACKAGE_THERM_INT_PLN_ENABLE;
- wrmsr_on_cpu(cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT, l, h);
+ smp_call_function_single(cpu, power_limit_irq_save_cpu, rp, 1);
+}
+
+static void power_limit_irq_restore_cpu(void *info)
+{
+ u32 l, h = 0;
+ struct rapl_package *rp = (struct rapl_package *)info;
+
+ rdmsr_safe(MSR_IA32_PACKAGE_THERM_INTERRUPT, &l, &h);
+
+ if (rp->power_limit_irq & PACKAGE_THERM_INT_PLN_ENABLE)
+ l |= PACKAGE_THERM_INT_PLN_ENABLE;
+ else
+ l &= ~PACKAGE_THERM_INT_PLN_ENABLE;
+
+ wrmsr_safe(MSR_IA32_PACKAGE_THERM_INTERRUPT, l, h);
}

/* restore per package power limit interrupt enable state */
static void package_power_limit_irq_restore(int package_id)
{
- u32 l, h;
int cpu;
struct rapl_package *rp;

@@ -951,14 +964,8 @@ static void package_power_limit_irq_restore(int package_id)
/* irq enable state not saved, nothing to restore */
if (!(rp->power_limit_irq & PACKAGE_PLN_INT_SAVED))
return;
- rdmsr_safe_on_cpu(cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT, &l, &h);
-
- if (rp->power_limit_irq & PACKAGE_THERM_INT_PLN_ENABLE)
- l |= PACKAGE_THERM_INT_PLN_ENABLE;
- else
- l &= ~PACKAGE_THERM_INT_PLN_ENABLE;

- wrmsr_on_cpu(cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT, l, h);
+ smp_call_function_single(cpu, power_limit_irq_restore_cpu, rp, 1);
}

static void set_floor_freq_default(struct rapl_domain *rd, bool mode)
--
1.9.1