change the semantic for calculating when to grow the size of a cache list.

previously it would figure out if there's enough items overall for
all the cpus to have full active an inactive free lists. this
included currently allocated items, which pools wont actually hold
on a free list and cannot predict when they will come back.

instead, see if there's enough items in the idle lists in the depot
that could instead go on all the free lists on the cpus. if there's
enough idle items, then we can grow.

tested by hrvoje popovski and amit kulkarni
ok visa@

1 files changed, 8 insertions, 14 deletions

diff --git a/sys/kern/subr_pool.c b/sys/kern/subr_pool.c
index 72d73633dfc..f2af8219c44 100644
--- a/sys/kern/subr_pool.c
+++ b/sys/kern/subr_pool.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: subr_pool.c,v 1.215 2017/06/19 23:57:12 dlg Exp $	*/
+/*	$OpenBSD: subr_pool.c,v 1.216 2017/06/23 01:02:18 dlg Exp $	*/
 /*	$NetBSD: subr_pool.c,v 1.61 2001/09/26 07:14:56 chs Exp $	*/
 
 /*-
@@ -1647,7 +1647,7 @@ pool_cache_init(struct pool *pp)
 	mtx_init(&pp->pr_cache_mtx, pp->pr_ipl);
 	arc4random_buf(pp->pr_cache_magic, sizeof(pp->pr_cache_magic));
 	TAILQ_INIT(&pp->pr_cache_lists);
-	pp->pr_cache_nlist = 0;
+	pp->pr_cache_nitems = 0;
 	pp->pr_cache_tick = ticks;
 	pp->pr_cache_items = 8;
 	pp->pr_cache_contention = 0;
@@ -1729,7 +1729,7 @@ pool_cache_list_alloc(struct pool *pp, struct pool_cache *pc)
 	pl = TAILQ_FIRST(&pp->pr_cache_lists);
 	if (pl != NULL) {
 		TAILQ_REMOVE(&pp->pr_cache_lists, pl, ci_nextl);
-		pp->pr_cache_nlist--;
+		pp->pr_cache_nitems -= POOL_CACHE_ITEM_NITEMS(pl);
 
 		pool_cache_item_magic(pp, pl);
 
@@ -1753,8 +1753,8 @@ pool_cache_list_free(struct pool *pp, struct pool_cache *pc,
 	if (TAILQ_EMPTY(&pp->pr_cache_lists))
 		pp->pr_cache_tick = ticks;
 
+	pp->pr_cache_nitems += POOL_CACHE_ITEM_NITEMS(ci);
 	TAILQ_INSERT_TAIL(&pp->pr_cache_lists, ci, ci_nextl);
-	pp->pr_cache_nlist++;
 
 	pc->pc_nlput++;
 
@@ -1936,8 +1936,8 @@ pool_cache_gc(struct pool *pp)
 		pl = TAILQ_FIRST(&pp->pr_cache_lists);
 		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_nlist--;
 
 			pp->pr_cache_ngc++;
 		}
@@ -1955,14 +1955,8 @@ pool_cache_gc(struct pool *pp)
 
 	contention = pp->pr_cache_contention;
 	if ((contention - pp->pr_cache_contention_prev) > 8 /* magic */) {
-		unsigned int limit = pp->pr_npages * pp->pr_itemsperpage;
-		unsigned int items = pp->pr_cache_items + 8;
-		unsigned int cache = ncpusfound * items * 2;
-
-		/* are there enough items around so every cpu can hold some? */
-
-		if (cache < limit)
-			pp->pr_cache_items = items;
+		if ((ncpusfound * 8 * 2) <= pp->pr_cache_nitems)
+			pp->pr_cache_items += 8;
 	}
 	pp->pr_cache_contention_prev = contention;
 }
@@ -2016,7 +2010,7 @@ pool_cache_info(struct pool *pp, void *oldp, size_t *oldlenp)
 	mtx_enter(&pp->pr_cache_mtx);
 	kpc.pr_ngc = pp->pr_cache_ngc;
 	kpc.pr_len = pp->pr_cache_items;
-	kpc.pr_nlist = pp->pr_cache_nlist;
+	kpc.pr_nitems = pp->pr_cache_nitems;
 	kpc.pr_contention = pp->pr_cache_contention;
 	mtx_leave(&pp->pr_cache_mtx);