On 22.7.2021 6.58, Li RongQing wrote:
SMT siblings share caches and other hardware, halt polling
will degrade its sibling performance if its sibling is busy
Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
---
include/linux/kvm_host.h | 5 ++++-
include/linux/sched.h | 17 +++++++++++++++++
kernel/sched/fair.c | 17 -----------------
3 files changed, 21 insertions(+), 18 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index ae7735b..15b3ef4 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -269,7 +269,10 @@ static inline bool kvm_vcpu_mapped(struct kvm_host_map *map)
static inline bool kvm_vcpu_can_poll(ktime_t cur, ktime_t stop)
{
- return single_task_running() && !need_resched() && ktime_before(cur, stop);
+ return single_task_running() &&
+ !need_resched() &&
+ ktime_before(cur, stop) &&
+ is_core_idle(raw_smp_processor_id());
}
/*
diff --git a/include/linux/sched.h b/include/linux/sched.h
index ec8d07d..c333218 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -34,6 +34,7 @@
#include <linux/rseq.h>
#include <linux/seqlock.h>
#include <linux/kcsan.h>
+#include <linux/topology.h>
#include <asm/kmap_size.h>
/* task_struct member predeclarations (sorted alphabetically): */
@@ -2191,6 +2192,22 @@ int sched_trace_rq_nr_running(struct rq *rq);
const struct cpumask *sched_trace_rd_span(struct root_domain *rd);
+static inline bool is_core_idle(int cpu)
+{
+#ifdef CONFIG_SCHED_SMT
+ int sibling;
+
+ for_each_cpu(sibling, cpu_smt_mask(cpu)) {
+ if (cpu == sibling)
+ continue;
+
+ if (!idle_cpu(cpu))
+ return false;
if (!idle_cpu(sibling)) instead, now it returns always false.
+ }
+#endif
+ return true;
+}
+
#ifdef CONFIG_SCHED_CORE
extern void sched_core_free(struct task_struct *tsk);
extern void sched_core_fork(struct task_struct *p);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 44c4520..5b0259c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1477,23 +1477,6 @@ struct numa_stats {
int idle_cpu;
};
-static inline bool is_core_idle(int cpu)
-{
-#ifdef CONFIG_SCHED_SMT
- int sibling;
-
- for_each_cpu(sibling, cpu_smt_mask(cpu)) {
- if (cpu == sibling)
- continue;
-
- if (!idle_cpu(cpu))
- return false;
- }
-#endif
-
- return true;
-}
-
struct task_numa_env {
struct task_struct *p;
