pool(9): remove ticks

Change the pool(9) timeouts to use the system uptime instead of ticks.

- Change the timeouts from variables to macros so we can use
  SEC_TO_NSEC().  This means these timeouts are no longer patchable
  via ddb(4).  dlg@ does not think this will be a problem, as the
  timeout intervals have not changed in years.

- Use low-res time to keep things fast.  Add a local copy of
  getnsecuptime() to subr_pool.c to keep the diff small.  We will need
  to move getnsecuptime() into kern_tc.c and document it later if we
  ever have other users elsewhere in the kernel.

- Rename ph_tick -> ph_timestamp and pr_cache_tick -> pr_cache_timestamp.

Prompted by tedu@ some time ago, but the effort stalled (may have been
my fault).  Input from kettenis@ and dlg@.

Special thanks to mpi@ for help with struct shuffling.  This change
does not increase the size of struct pool_page_header or struct pool.

ok dlg@ mpi@

2 files changed, 29 insertions, 14 deletions

diff --git a/sys/kern/subr_pool.c b/sys/kern/subr_pool.c
index a2c941567f9..a233ff5bd8e 100644
--- a/sys/kern/subr_pool.c
+++ b/sys/kern/subr_pool.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: subr_pool.c,v 1.230 2020/01/24 06:31:17 cheloha Exp $	*/
+/*	$OpenBSD: subr_pool.c,v 1.231 2021/01/02 03:23:59 cheloha Exp $	*/
 /*	$NetBSD: subr_pool.c,v 1.61 2001/09/26 07:14:56 chs Exp $	*/
 
 /*-
@@ -41,6 +41,7 @@
 #include <sys/syslog.h>
 #include <sys/sysctl.h>
 #include <sys/task.h>
+#include <sys/time.h>
 #include <sys/timeout.h>
 #include <sys/percpu.h>
 
@@ -148,7 +149,7 @@ struct pool_page_header {
 	caddr_t			ph_page;	/* this page's address */
 	caddr_t			ph_colored;	/* page's colored address */
 	unsigned long		ph_magic;
-	int			ph_tick;
+	uint64_t		ph_timestamp;
 };
 #define POOL_MAGICBIT (1 << 3) /* keep away from perturbed low bits */
 #define POOL_PHPOISON(ph) ISSET((ph)->ph_magic, POOL_MAGICBIT)
@@ -266,8 +267,22 @@ void	pool_gc_sched(void *);
 struct timeout pool_gc_tick = TIMEOUT_INITIALIZER(pool_gc_sched, NULL);
 void	pool_gc_pages(void *);
 struct task pool_gc_task = TASK_INITIALIZER(pool_gc_pages, NULL);
-int pool_wait_free = 1;
-int pool_wait_gc = 8;
+
+#define POOL_WAIT_FREE	SEC_TO_NSEC(1)
+#define POOL_WAIT_GC	SEC_TO_NSEC(8)
+
+/*
+ * TODO Move getnsecuptime() to kern_tc.c and document it when we
+ * have callers in other modules.
+ */
+static uint64_t
+getnsecuptime(void)
+{
+	struct timespec now;
+
+	getnanouptime(&now);
+	return TIMESPEC_TO_NSEC(&now);
+}
 
 RBT_PROTOTYPE(phtree, pool_page_header, ph_node, phtree_compare);
 
@@ -797,7 +812,7 @@ pool_put(struct pool *pp, void *v)
 	/* is it time to free a page? */
 	if (pp->pr_nidle > pp->pr_maxpages &&
 	    (ph = TAILQ_FIRST(&pp->pr_emptypages)) != NULL &&
-	    (ticks - ph->ph_tick) > (hz * pool_wait_free)) {
+	    getnsecuptime() - ph->ph_timestamp > POOL_WAIT_FREE) {
 		freeph = ph;
 		pool_p_remove(pp, freeph);
 	}
@@ -864,7 +879,7 @@ pool_do_put(struct pool *pp, void *v)
 		 */
 		pp->pr_nidle++;
 
-		ph->ph_tick = ticks;
+		ph->ph_timestamp = getnsecuptime();
 		TAILQ_REMOVE(&pp->pr_partpages, ph, ph_entry);
 		TAILQ_INSERT_TAIL(&pp->pr_emptypages, ph, ph_entry);
 		pool_update_curpage(pp);
@@ -1566,7 +1581,7 @@ pool_gc_pages(void *null)
 		/* is it time to free a page? */
 		if (pp->pr_nidle > pp->pr_minpages &&
 		    (ph = TAILQ_FIRST(&pp->pr_emptypages)) != NULL &&
-		    (ticks - ph->ph_tick) > (hz * pool_wait_gc)) {
+		    getnsecuptime() - ph->ph_timestamp > POOL_WAIT_GC) {
 			freeph = ph;
 			pool_p_remove(pp, freeph);
 		} else
@@ -1726,7 +1741,7 @@ pool_cache_init(struct pool *pp)
 	arc4random_buf(pp->pr_cache_magic, sizeof(pp->pr_cache_magic));
 	TAILQ_INIT(&pp->pr_cache_lists);
 	pp->pr_cache_nitems = 0;
-	pp->pr_cache_tick = ticks;
+	pp->pr_cache_timestamp = getnsecuptime();
 	pp->pr_cache_items = 8;
 	pp->pr_cache_contention = 0;
 	pp->pr_cache_ngc = 0;
@@ -1829,7 +1844,7 @@ pool_cache_list_free(struct pool *pp, struct pool_cache *pc,
 {
 	pool_list_enter(pp);
 	if (TAILQ_EMPTY(&pp->pr_cache_lists))
-		pp->pr_cache_tick = ticks;
+		pp->pr_cache_timestamp = getnsecuptime();
 
 	pp->pr_cache_nitems += POOL_CACHE_ITEM_NITEMS(ci);
 	TAILQ_INSERT_TAIL(&pp->pr_cache_lists, ci, ci_nextl);
@@ -2006,7 +2021,7 @@ pool_cache_gc(struct pool *pp)
 {
 	unsigned int contention, delta;
 
-	if ((ticks - pp->pr_cache_tick) > (hz * pool_wait_gc) &&
+	if (getnsecuptime() - pp->pr_cache_timestamp > POOL_WAIT_GC &&
 	    !TAILQ_EMPTY(&pp->pr_cache_lists) &&
 	    pl_enter_try(pp, &pp->pr_cache_lock)) {
 		struct pool_cache_item *pl = NULL;
@@ -2015,7 +2030,7 @@ pool_cache_gc(struct pool *pp)
 		if (pl != NULL) {
 			TAILQ_REMOVE(&pp->pr_cache_lists, pl, ci_nextl);
 			pp->pr_cache_nitems -= POOL_CACHE_ITEM_NITEMS(pl);
-			pp->pr_cache_tick = ticks;
+			pp->pr_cache_timestamp = getnsecuptime();
 
 			pp->pr_cache_ngc++;
 		}
diff --git a/sys/sys/pool.h b/sys/sys/pool.h
index 7f68d50c5ea..3e64c3c34e5 100644
--- a/sys/sys/pool.h
+++ b/sys/sys/pool.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pool.h,v 1.77 2019/07/19 09:03:03 bluhm Exp $	*/
+/*	$OpenBSD: pool.h,v 1.78 2021/01/02 03:23:59 cheloha Exp $	*/
 /*	$NetBSD: pool.h,v 1.27 2001/06/06 22:00:17 rafal Exp $	*/
 
 /*-
@@ -201,9 +201,9 @@ struct pool {
 	u_int		pr_cache_items;	/* target list length */
 	u_int		pr_cache_contention;
 	u_int		pr_cache_contention_prev;
-	int		pr_cache_tick;	/* time idle list was empty */
-	int		pr_cache_nout;
+	uint64_t	pr_cache_timestamp;	/* time idle list was empty */
 	uint64_t	pr_cache_ngc;	/* # of times the gc released a list */
+	int		pr_cache_nout;
 
 	u_int		pr_align;
 	u_int		pr_maxcolors;	/* Cache coloring */