For SPLPAR, lparcfg provides a sum of PURR registers for all CPUs.
Currently this is done by reading PURR in context switch and timer
interrupt, and storing that into a per-CPU variable. These are summed
to provide the value.
This does not work with all timer schemes (e.g., NO_HZ_FULL), and it
is sub-optimal for performance because it reads the PURR register on
every context switch, although that's been difficult to distinguish
from noise in the contxt_switch microbenchmark.
This patch implements the sum by calling a function on each CPU, to
read and add PURR values of each CPU.
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
arch/powerpc/include/asm/time.h | 8 --------
arch/powerpc/kernel/process.c | 14 --------------
arch/powerpc/kernel/time.c | 8 --------
arch/powerpc/platforms/pseries/lparcfg.c | 18 ++++++++++--------
4 files changed, 10 insertions(+), 38 deletions(-)
diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/time.h
index db546c034905..c965c79765c4 100644
--- a/arch/powerpc/include/asm/time.h
+++ b/arch/powerpc/include/asm/time.h
@@ -196,14 +196,6 @@ extern u64 mulhdu(u64, u64);
extern void div128_by_32(u64 dividend_high, u64 dividend_low,
unsigned divisor, struct div_result *dr);
-/* Used to store Processor Utilization register (purr) values */
-
-struct cpu_usage {
- u64 current_tb; /* Holds the current purr register values */
-};
-
-DECLARE_PER_CPU(struct cpu_usage, cpu_usage_array);
-
extern void secondary_cpu_time_init(void);
extern void __init time_init(void);
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index ff7344d996e3..e6ff36923d84 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -845,10 +845,6 @@ bool ppc_breakpoint_available(void)
}
EXPORT_SYMBOL_GPL(ppc_breakpoint_available);
-#ifdef CONFIG_PPC64
-DEFINE_PER_CPU(struct cpu_usage, cpu_usage_array);
-#endif
-
static inline bool hw_brk_match(struct arch_hw_breakpoint *a,
struct arch_hw_breakpoint *b)
{
@@ -1181,16 +1177,6 @@ struct task_struct *__switch_to(struct task_struct *prev,
WARN_ON(!irqs_disabled());
-#ifdef CONFIG_PPC64
- /*
- * Collect processor utilization data per process
- */
- if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
- struct cpu_usage *cu = this_cpu_ptr(&cpu_usage_array);
- cu->current_tb = mfspr(SPRN_PURR);
- }
-#endif /* CONFIG_PPC64 */
-
#ifdef CONFIG_PPC_BOOK3S_64
batch = this_cpu_ptr(&ppc64_tlb_batch);
if (batch->active) {
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index e7e8611e8863..1fe6a24357e7 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -597,14 +597,6 @@ static void __timer_interrupt(void)
__this_cpu_inc(irq_stat.timer_irqs_others);
}
-#ifdef CONFIG_PPC64
- /* collect purr register values often, for accurate calculations */
- if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
- struct cpu_usage *cu = this_cpu_ptr(&cpu_usage_array);
- cu->current_tb = mfspr(SPRN_PURR);
- }
-#endif
-
trace_timer_interrupt_exit(regs);
}
diff --git a/arch/powerpc/platforms/pseries/lparcfg.c
b/arch/powerpc/platforms/pseries/lparcfg.c
index c508c938dc71..7c872dc01bdb 100644
--- a/arch/powerpc/platforms/pseries/lparcfg.c
+++ b/arch/powerpc/platforms/pseries/lparcfg.c
@@ -52,18 +52,20 @@
* Track sum of all purrs across all processors. This is used to further
* calculate usage values by different applications
*/
+static void cpu_get_purr(void *arg)
+{
+ atomic64_t *sum = arg;
+
+ atomic64_add(mfspr(SPRN_PURR), sum);
+}
+
static unsigned long get_purr(void)
{
- unsigned long sum_purr = 0;
- int cpu;
+ atomic64_t purr = ATOMIC64_INIT(0);
- for_each_possible_cpu(cpu) {
- struct cpu_usage *cu;
+ on_each_cpu(cpu_get_purr, &purr, 1);
- cu = &per_cpu(cpu_usage_array, cpu);
- sum_purr += cu->current_tb;
- }
- return sum_purr;
+ return atomic64_read(&purr);
}
/*
--
2.17.0
