Index: subr_percpu.c
===================================================================
RCS file: /cvs/src/sys/kern/subr_percpu.c,v
retrieving revision 1.9
diff -u -p -r1.9 subr_percpu.c
--- subr_percpu.c	10 Mar 2021 10:21:47 -0000	1.9
+++ subr_percpu.c	14 Mar 2022 01:26:17 -0000
@@ -16,6 +16,8 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include "kstat.h"
+
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/pool.h>
@@ -26,9 +28,103 @@
 #ifdef MULTIPROCESSOR
 struct pool cpumem_pl;
 
+#if NKSTAT > 0
+#include <sys/kstat.h>
+#include <sys/task.h>
+#include <sys/proc.h>
+
+struct pinger {
+	struct cpu_info	*ci;
+	struct taskq	*tq;
+	struct kstat	*ks;
+	struct task	 peg;
+};
+
+static struct pinger *pingers;
+
+static int
+pinger_kstat(struct kstat *ks)
+{
+	struct kstat_kv *kvs = ks->ks_data;
+	struct cond c;
+	struct task t = TASK_INITIALIZER((void *)cond_signal, &c);
+	unsigned int i;
+
+	getnanouptime(&ks->ks_updated);
+
+	for (i = 0; i < ncpus; i++) {
+		struct kstat_kv *kv = &kvs[i];
+		struct pinger *p = &pingers[i];
+		uint64_t tic, toc;
+
+		cond_init(&c);
+
+		tic = rdtsc();
+		task_add(p->tq, &t);
+		cond_wait(&c, "pinger");
+		toc = rdtsc();
+
+		kstat_kv_u64(kv) = toc - tic;
+	}
+
+	return (0);
+}
+
+static void
+pinger_init(struct pinger *p, struct cpu_info *ci)
+{
+	struct kstat *ks;
+	struct kstat_kv *kvs;
+	unsigned int i;
+
+	KASSERT(p->ci == NULL);
+
+	p->ci = ci;
+	p->tq = taskq_create(ci->ci_dev->dv_xname, 1,
+	    IPL_SOFTNET, TASKQ_MPSAFE);
+
+	task_set(&p->peg, (void *)sched_peg_curproc, ci);
+	task_add(p->tq, &p->peg);
+
+	ks = kstat_create("pinger", 0, "cpu", ci->ci_cpuid, KSTAT_T_KV, 0);
+	if (ks == NULL)
+		panic("%s kstat_create", __func__);
+
+	kvs = mallocarray(sizeof(*kvs), ncpus, M_DEVBUF,
+	    M_WAITOK|M_ZERO);
+	for (i = 0; i < ncpus; i++) {
+		struct kstat_kv *kv = &kvs[i];
+
+		snprintf(kv->kv_key, sizeof(kv->kv_key), "cpu%u", i);
+		kv->kv_type = KSTAT_KV_T_UINT64;
+		kv->kv_unit = KSTAT_KV_U_CYCLES;
+	}
+
+	ks->ks_data = kvs;
+	ks->ks_datalen = sizeof(*kvs) * ncpus;
+	ks->ks_read = pinger_kstat;
+
+	kstat_install(ks);
+
+	p->ks = ks;
+}
+#endif /* NKSTAT > 0 */
+
 void
 percpu_init(void)
 {
+#if NKSTAT > 0
+	CPU_INFO_ITERATOR cii;
+	struct cpu_info *ci;
+
+	pingers = mallocarray(sizeof(*pingers), ncpus, M_DEVBUF,
+	    M_WAITOK|M_ZERO);
+	CPU_INFO_FOREACH(cii, ci) {
+		KASSERT(ci->ci_cpuid < ncpus);
+		pinger_init(&pingers[ci->ci_cpuid], ci);
+	}
+#endif /* NKSTAT > 0 */
+
 	pool_init(&cpumem_pl, sizeof(struct cpumem) * ncpusfound, 0,
 	    IPL_NONE, PR_WAITOK, "percpumem", &pool_allocator_single);
 }