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Index: sys/kern/sched_ule.c
===================================================================
--- sys/kern/sched_ule.c
+++ sys/kern/sched_ule.c
@@ -251,6 +251,7 @@
struct runq tdq_realtime; /* real-time run queue. */
struct runq tdq_timeshare; /* timeshare run queue. */
struct runq tdq_idle; /* Queue of IDLE threads. */
+ sbintime_t tdq_next_steal; /* When can we attempt to steal. */
char tdq_name[TDQ_NAME_LEN];
#ifdef KTR
char tdq_loadname[TDQ_LOADNAME_LEN];
@@ -277,6 +278,7 @@
static int __read_mostly steal_thresh = 2;
static int __read_mostly always_steal = 0;
static int __read_mostly trysteal_limit = 2;
+static int __read_mostly steal_interval;
/*
* One thread queue per processor.
@@ -976,6 +978,22 @@
return (td);
}
+#ifdef SMP
+static bool
+tdq_can_steal(struct tdq *tdq)
+{
+ sbintime_t now;
+
+ if (steal_interval != 0) {
+ now = getsbinuptime();
+ if (now < tdq->tdq_next_steal)
+ return (false);
+ tdq->tdq_next_steal = now + steal_interval * SBT_1US;
+ }
+ return (true);
+}
+#endif
+
/*
* This tdq has idled. Try to steal a thread from another cpu and switch
* to it.
@@ -990,6 +1008,10 @@
if (smp_started == 0 || steal_idle == 0 || tdq->tdq_cg == NULL)
return (1);
+#ifdef SMP
+ if (!tdq_can_steal(tdq))
+ return (1);
+#endif
CPU_FILL(&mask);
CPU_CLR(PCPU_GET(cpuid), &mask);
restart:
@@ -1923,7 +1945,8 @@
cpuset_t mask;
int cpu, i;
- if (smp_started == 0 || trysteal_limit == 0 || tdq->tdq_cg == NULL)
+ if (smp_started == 0 || trysteal_limit == 0 || tdq->tdq_cg == NULL ||
+ !tdq_can_steal(tdq))
return;
CPU_FILL(&mask);
CPU_CLR(PCPU_GET(cpuid), &mask);
@@ -3121,6 +3144,9 @@
0, "Topological distance limit for stealing threads in sched_switch()");
SYSCTL_INT(_kern_sched, OID_AUTO, always_steal, CTLFLAG_RW, &always_steal, 0,
"Always run the stealer from the idle thread");
+SYSCTL_INT(_kern_sched, OID_AUTO, steal_interval, CTLFLAG_RWTUN,
+ &steal_interval, 0,
+ "Steal work only every steal_interval microseconds");
SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
CTLFLAG_MPSAFE | CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
"XML dump of detected CPU topology");

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