available_cores - Number of cores LPAR(VM) can use at this moment.
remaining cores will have CPUs marked as paravirt.
This follow stepwise approach for reducing/increasing the number of
available_cores.
Very simple Logic.
if (steal_time > high_threshold)
available_cores--
if (steal_time < low_threshould)
available_cores++
It also check previous direction taken to avoid un-necessary ping-pongs.
Note: It works well only when CPUs are spread out equal numbered across
NUMA nodes.
Originally-by: Srikar Dronamraju <[email protected]>
Signed-off-by: Shrikanth Hegde <[email protected]>
---
arch/powerpc/platforms/pseries/lpar.c | 53 ++++++++++++++++++++++++
arch/powerpc/platforms/pseries/pseries.h | 1 +
2 files changed, 54 insertions(+)
diff --git a/arch/powerpc/platforms/pseries/lpar.c
b/arch/powerpc/platforms/pseries/lpar.c
index 935fced6e127..825b5b4e2b43 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -43,6 +43,7 @@
#include <asm/fadump.h>
#include <asm/dtl.h>
#include <asm/vphn.h>
+#include <linux/sched/isolation.h>
#include "pseries.h"
@@ -2056,6 +2057,58 @@ void pseries_init_ec_vp_cores(void)
/* Initialize the available cores to all VP initially */
available_cores = max(entitled_cores, virtual_procs);
}
+
+#define STEAL_RATIO_HIGH 400
+#define STEAL_RATIO_LOW 150
+
+void update_soft_entitlement(unsigned long steal_ratio)
+{
+ static int prev_direction;
+ int cpu;
+
+ if (!entitled_cores)
+ return;
+
+ if (steal_ratio >= STEAL_RATIO_HIGH && prev_direction > 0) {
+ /*
+ * System entitlement was reduced earlier but we continue to
+ * see steal time. Reduce entitlement further.
+ */
+ if (available_cores == entitled_cores)
+ return;
+
+ /* Mark them paravirt, enable tick if it is nohz_full */
+ for (cpu = (available_cores - 1) * threads_per_core;
+ cpu < available_cores * threads_per_core; cpu++) {
+ set_cpu_paravirt(cpu, true);
+ if (tick_nohz_full_cpu(cpu))
+ tick_nohz_dep_set_cpu(cpu, TICK_DEP_BIT_SCHED);
+ }
+ available_cores--;
+
+ } else if (steal_ratio <= STEAL_RATIO_LOW && prev_direction < 0) {
+ /*
+ * System entitlement was increased but we continue to see
+ * less steal time. Increase entitlement further.
+ */
+ if (available_cores == virtual_procs)
+ return;
+
+ /* mark them avaialble */
+ for (cpu = available_cores * threads_per_core;
+ cpu < (available_cores + 1) * threads_per_core; cpu++)
+ set_cpu_paravirt(cpu, false);
+
+ available_cores++;
+ }
+ if (steal_ratio >= STEAL_RATIO_HIGH)
+ prev_direction = 1;
+ else if (steal_ratio <= STEAL_RATIO_LOW)
+ prev_direction = -1;
+ else
+ prev_direction = 0;
+}
#else
void pseries_init_ec_vp_cores(void) { return; }
+void update_soft_entitlement(unsigned long steal_ratio) { return; }
#endif
diff --git a/arch/powerpc/platforms/pseries/pseries.h
b/arch/powerpc/platforms/pseries/pseries.h
index 3968a6970fa8..d1f9ec77ff57 100644
--- a/arch/powerpc/platforms/pseries/pseries.h
+++ b/arch/powerpc/platforms/pseries/pseries.h
@@ -115,6 +115,7 @@ int dlpar_workqueue_init(void);
extern u32 pseries_security_flavor;
void pseries_setup_security_mitigations(void);
+void update_soft_entitlement(unsigned long steal_ratio);
#ifdef CONFIG_PPC_64S_HASH_MMU
void pseries_lpar_read_hblkrm_characteristics(void);
--
2.47.3
