mpi@ suggests folding the pseudorandom advance code from
clockintr_statclock() into the clockintr API itself. This replaces
three API calls -- clockintr_expiration(), clockintr_nsecuptime(), and
clockintr_schedule() -- we just one call to a new function,
clockintr_advance_random().
I'm fine with it. A pseudorandom period is an odd thing and
supporting it is difficult. Having a single bespoke API to support it
might be the lesser of two evils.
With this in place, the statclock() patch on tech@ can be simplified.
ok?
Index: kern_clockintr.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_clockintr.c,v
retrieving revision 1.33
diff -u -p -r1.33 kern_clockintr.c
--- kern_clockintr.c 26 Aug 2023 22:21:00 -0000 1.33
+++ kern_clockintr.c 5 Sep 2023 14:11:38 -0000
@@ -42,8 +42,8 @@ uint32_t statclock_avg; /* [I] average
uint32_t statclock_min; /* [I] minimum statclock period
(ns) */
uint32_t statclock_mask; /* [I] set of allowed offsets */
+uint64_t clockintr_advance_random(struct clockintr *, uint64_t, uint32_t);
void clockintr_cancel_locked(struct clockintr *);
-uint64_t clockintr_expiration(const struct clockintr *);
void clockintr_hardclock(struct clockintr *, void *);
uint64_t clockintr_nsecuptime(const struct clockintr *);
void clockintr_schedule(struct clockintr *, uint64_t);
@@ -345,6 +345,30 @@ clockintr_advance(struct clockintr *cl,
return count;
}
+/*
+ * Custom version of clockintr_advance() to support a pseudorandom
+ * statclock() period. Hopefully we can throw this out at some point
+ * in the future.
+ */
+uint64_t
+clockintr_advance_random(struct clockintr *cl, uint64_t lo, uint32_t mask)
+{
+ uint64_t count = 0;
+ struct clockintr_queue *cq = cl->cl_queue;
+ uint32_t off;
+
+ KASSERT(cl == &cq->cq_shadow);
+
+ while (cl->cl_expiration <= cq->cq_uptime) {
+ while ((off = (random() & mask)) == 0)
+ continue;
+ cl->cl_expiration += lo + off;
+ count++;
+ }
+ SET(cl->cl_flags, CLST_SHADOW_PENDING);
+ return count;
+}
+
void
clockintr_cancel(struct clockintr *cl)
{
@@ -402,21 +426,6 @@ clockintr_establish(struct clockintr_que
return cl;
}
-uint64_t
-clockintr_expiration(const struct clockintr *cl)
-{
- uint64_t expiration;
- struct clockintr_queue *cq = cl->cl_queue;
-
- if (cl == &cq->cq_shadow)
- return cl->cl_expiration;
-
- mtx_enter(&cq->cq_mtx);
- expiration = cl->cl_expiration;
- mtx_leave(&cq->cq_mtx);
- return expiration;
-}
-
void
clockintr_schedule(struct clockintr *cl, uint64_t expiration)
{
@@ -478,13 +487,6 @@ clockintr_stagger(struct clockintr *cl,
mtx_leave(&cq->cq_mtx);
}
-uint64_t
-clockintr_nsecuptime(const struct clockintr *cl)
-{
- KASSERT(cl == &cl->cl_queue->cq_shadow);
- return cl->cl_queue->cq_uptime;
-}
-
void
clockintr_hardclock(struct clockintr *cl, void *frame)
{
@@ -498,20 +500,11 @@ clockintr_hardclock(struct clockintr *cl
void
clockintr_statclock(struct clockintr *cl, void *frame)
{
- uint64_t count, expiration, i, uptime;
- uint32_t off;
+ uint64_t count, i;
if (ISSET(clockintr_flags, CL_RNDSTAT)) {
- count = 0;
- expiration = clockintr_expiration(cl);
- uptime = clockintr_nsecuptime(cl);
- while (expiration <= uptime) {
- while ((off = (random() & statclock_mask)) == 0)
- continue;
- expiration += statclock_min + off;
- count++;
- }
- clockintr_schedule(cl, expiration);
+ count = clockintr_advance_random(cl, statclock_min,
+ statclock_mask);
} else {
count = clockintr_advance(cl, statclock_avg);
}
