From: "Gautham R. Shenoy" <[email protected]>
On Pseries LPARs, to calculate utilization, we need to know the
[S]PURR ticks when the CPUs were busy or idle.
Via idle_loop_prolog(), idle_loop_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 <[email protected]>
---
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 126a217..db82fc1 100644
--- a/arch/powerpc/include/asm/idle.h
+++ b/arch/powerpc/include/asm/idle.h
@@ -2,13 +2,20 @@
#define _ASM_POWERPC_IDLE_H
#include <asm/runlatch.h>
+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;
@@ -19,10 +26,19 @@ 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 idle_loop_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.
@@ -33,6 +49,7 @@ static inline void idle_loop_prolog(void)
static inline void idle_loop_epilog(void)
{
update_idle_purr_accounting();
+ update_idle_spurr_accounting();
get_lppaca()->idle = 0;
ppc64_runlatch_on();
}
@@ -52,4 +69,20 @@ 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
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index e9f2cefa..5ef5c82 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
"Gautham R. Shenoy" <[email protected]> writes:
> +static inline void snapshot_spurr_idle_entry(void)
> +{
> + *this_cpu_ptr(&idle_entry_spurr_snap) = mfspr(SPRN_SPURR);
> +}
> +
[...]
> +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 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();
This samples spurr twice when it could do with just one. I don't know
the performance implications, but will the results be coherent?
Hello Nathan,
On Fri, Feb 21, 2020 at 10:47:41AM -0600, Nathan Lynch wrote:
> "Gautham R. Shenoy" <[email protected]> writes:
> > +static inline void snapshot_spurr_idle_entry(void)
> > +{
> > + *this_cpu_ptr(&idle_entry_spurr_snap) = mfspr(SPRN_SPURR);
> > +}
> > +
>
> [...]
>
> > +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 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();
>
> This samples spurr twice when it could do with just one. I don't know
> the performance implications, but will the results be coherent?
We would have taken the snapshot in idle_loop_prolog() just before
entering idle. That fact that the "if" condition is true above in
read_this_idle_spurr() implies that we are reading the idle_spurr
value from an interrupt context and since get_lppaca()->idle == 1, we
haven't yet called idle_loop_epilog(), where we would have updated the
idle_spurr ticks for the last idle period.
Hence, in this function, we first update the idle_spurr accounting
from the time of the last snapshot to now. We update the snapshot to
the current SPURR value so that when we eventually call
idle_loop_epilog(), we will account for the remaining idle duration,
i.e from the read_this_idle_spurr() call to idle_loop_epilog()
The results are therefore coherant, in that we do not perform double
accounting the second time we invoke update_idle_spurr_accounting()
from idle_loop_epilog(), but only add the spurr ticks from
read_this_idle_spurr() to idle_loop_epilog().
--
Thanks and Regards
gautham.