[PATCH v4 3/6] powerpc/pseries: Account for SPURR ticks on idle CPUs

Gautham R. Shenoy
2020-03-27T11:33:04Z

From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

On Pseries LPARs, to calculate utilization, we need to know the
[S]PURR ticks when the CPUs were busy or idle.

Via pseries_idle_prolog(), pseries_idle_epilog(), we track the idle
PURR ticks in the VPA variable "wait_state_cycles". This patch extends
the support to account for the idle SPURR ticks. It also provides an
accessor function to accurately reads idle SPURR ticks.

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
---
arch/powerpc/include/asm/idle.h | 33 +++++++++++++++++++++++++++++++++
arch/powerpc/platforms/pseries/setup.c | 2 ++
2 files changed, 35 insertions(+)

diff --git a/arch/powerpc/include/asm/idle.h b/arch/powerpc/include/asm/idle.h
index d4bfb6a..accd1f5 100644
--- a/arch/powerpc/include/asm/idle.h
+++ b/arch/powerpc/include/asm/idle.h
@@ -5,13 +5,20 @@
#include <asm/paca.h>

#ifdef CONFIG_PPC_PSERIES
+DECLARE_PER_CPU(u64, idle_spurr_cycles);
DECLARE_PER_CPU(u64, idle_entry_purr_snap);
+DECLARE_PER_CPU(u64, idle_entry_spurr_snap);

static inline void snapshot_purr_idle_entry(void)
{
*this_cpu_ptr(&idle_entry_purr_snap) = mfspr(SPRN_PURR);
}

+static inline void snapshot_spurr_idle_entry(void)
+{
+ *this_cpu_ptr(&idle_entry_spurr_snap) = mfspr(SPRN_SPURR);
+}
+
static inline void update_idle_purr_accounting(void)
{
u64 wait_cycles;
@@ -22,10 +29,19 @@ static inline void update_idle_purr_accounting(void)
get_lppaca()->wait_state_cycles = cpu_to_be64(wait_cycles);
}

+static inline void update_idle_spurr_accounting(void)
+{
+ u64 *idle_spurr_cycles_ptr = this_cpu_ptr(&idle_spurr_cycles);
+ u64 in_spurr = *this_cpu_ptr(&idle_entry_spurr_snap);
+
+ *idle_spurr_cycles_ptr += mfspr(SPRN_SPURR) - in_spurr;
+}
+
static inline void pseries_idle_prolog(void)
{
ppc64_runlatch_off();
snapshot_purr_idle_entry();
+ snapshot_spurr_idle_entry();
/*
* Indicate to the HV that we are idle. Now would be
* a good time to find other work to dispatch.
@@ -36,6 +52,7 @@ static inline void pseries_idle_prolog(void)
static inline void pseries_idle_epilog(void)
{
update_idle_purr_accounting();
+ update_idle_spurr_accounting();
get_lppaca()->idle = 0;
ppc64_runlatch_on();
}
@@ -56,5 +73,21 @@ static inline u64 read_this_idle_purr(void)
return be64_to_cpu(get_lppaca()->wait_state_cycles);
}

+static inline u64 read_this_idle_spurr(void)
+{
+ /*
+ * If we are reading from an idle context, update the
+ * idle-spurr cycles corresponding to the last idle period.
+ * Since the idle context is not yet over, take a fresh
+ * snapshot of the idle-spurr.
+ */
+ if (get_lppaca()->idle == 1) {
+ update_idle_spurr_accounting();
+ snapshot_spurr_idle_entry();
+ }
+
+ return *this_cpu_ptr(&idle_spurr_cycles);
+}
+
#endif /* CONFIG_PPC_PSERIES */
#endif
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 4905c96..1b55e80 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -318,7 +318,9 @@ static int alloc_dispatch_log_kmem_cache(void)
}
machine_early_initcall(pseries, alloc_dispatch_log_kmem_cache);

+DEFINE_PER_CPU(u64, idle_spurr_cycles);
DEFINE_PER_CPU(u64, idle_entry_purr_snap);
+DEFINE_PER_CPU(u64, idle_entry_spurr_snap);
static void pseries_lpar_idle(void)
{
/*
--
1.9.4