3537 add kstat_waitq_enter and friends

These kstat interfaces are required to port
"Illumos #3537 want pool io kstats" to ZFS on Linux.

kstat_waitq_enter()
kstat_waitq_exit()
kstat_runq_enter()
kstat_runq_exit()

Additionally, zero out the ks_data buffer in __kstat_create() so
that the kstat_io_t counters are initialized to zero.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

include/sys/kstat.h

@@ -189,6 +189,10 @@ extern kstat_t *__kstat_create(const char *ks_module, int ks_instance,
 			     uchar_t ks_flags);
 extern void __kstat_install(kstat_t *ksp);
 extern void __kstat_delete(kstat_t *ksp);
+extern void kstat_waitq_enter(kstat_io_t *);
+extern void kstat_waitq_exit(kstat_io_t *);
+extern void kstat_runq_enter(kstat_io_t *);
+extern void kstat_runq_exit(kstat_io_t *);
 
 #define kstat_set_raw_ops(k,h,d,a)	__kstat_set_raw_ops(k,h,d,a)
 #define kstat_create(m,i,n,c,t,s,f)	__kstat_create(m,i,n,c,t,s,f)

module/spl/spl-kstat.c

@@ -54,6 +54,72 @@ kstat_resize_raw(kstat_t *ksp)
 	return 0;
 }
 
+void
+kstat_waitq_enter(kstat_io_t *kiop)
+{
+	hrtime_t new, delta;
+	ulong_t wcnt;
+
+	new = gethrtime();
+	delta = new - kiop->wlastupdate;
+	kiop->wlastupdate = new;
+	wcnt = kiop->wcnt++;
+	if (wcnt != 0) {
+		kiop->wlentime += delta * wcnt;
+		kiop->wtime += delta;
+	}
+}
+EXPORT_SYMBOL(kstat_waitq_enter);
+
+void
+kstat_waitq_exit(kstat_io_t *kiop)
+{
+	hrtime_t new, delta;
+	ulong_t wcnt;
+
+	new = gethrtime();
+	delta = new - kiop->wlastupdate;
+	kiop->wlastupdate = new;
+	wcnt = kiop->wcnt--;
+	ASSERT((int)wcnt > 0);
+	kiop->wlentime += delta * wcnt;
+	kiop->wtime += delta;
+}
+EXPORT_SYMBOL(kstat_waitq_exit);
+
+void
+kstat_runq_enter(kstat_io_t *kiop)
+{
+	hrtime_t new, delta;
+	ulong_t rcnt;
+
+	new = gethrtime();
+	delta = new - kiop->rlastupdate;
+	kiop->rlastupdate = new;
+	rcnt = kiop->rcnt++;
+	if (rcnt != 0) {
+		kiop->rlentime += delta * rcnt;
+		kiop->rtime += delta;
+	}
+}
+EXPORT_SYMBOL(kstat_runq_enter);
+
+void
+kstat_runq_exit(kstat_io_t *kiop)
+{
+	hrtime_t new, delta;
+	ulong_t rcnt;
+
+	new = gethrtime();
+	delta = new - kiop->rlastupdate;
+	kiop->rlastupdate = new;
+	rcnt = kiop->rcnt--;
+	ASSERT((int)rcnt > 0);
+	kiop->rlentime += delta * rcnt;
+	kiop->rtime += delta;
+}
+EXPORT_SYMBOL(kstat_runq_exit);
+
 static int
 kstat_seq_show_headers(struct seq_file *f)
 {
@@ -539,7 +605,7 @@ __kstat_create(const char *ks_module, int ks_instance, const char *ks_name,
 	if (ksp->ks_flags & KSTAT_FLAG_VIRTUAL) {
                 ksp->ks_data = NULL;
         } else {
-                ksp->ks_data = kmem_alloc(ksp->ks_data_size, KM_SLEEP);
+                ksp->ks_data = kmem_zalloc(ksp->ks_data_size, KM_SLEEP);
                 if (ksp->ks_data == NULL) {
                         kmem_free(ksp, sizeof(*ksp));
                         ksp = NULL;