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Index: sys/vm/uma_core.c
===================================================================
--- sys/vm/uma_core.c
+++ sys/vm/uma_core.c
@@ -1415,6 +1415,64 @@
uma_total_dec(PAGE_SIZE * keg->uk_ppera);
}
+static void
+keg_drain_domain(uma_keg_t keg, int domain)
+{
+ struct slabhead freeslabs;
+ uma_domain_t dom;
+ uma_slab_t slab, tmp;
+ uint32_t i, stofree, stokeep, partial;
+
+ dom = &keg->uk_domain[domain];
+ LIST_INIT(&freeslabs);
+
+ CTR4(KTR_UMA, "keg_drain %s(%p) domain %d free items: %u",
+ keg->uk_name, keg, i, dom->ud_free_items);
+
+ KEG_LOCK(keg, domain);
+
+ /*
+ * Are the free items in partially allocated slabs sufficient to meet
+ * the reserve? If not, compute the number of fully free slabs that must
+ * be kept.
+ */
+ partial = dom->ud_free_items - dom->ud_free_slabs * keg->uk_ipers;
+ if (partial < keg->uk_reserve) {
+ stokeep = min(dom->ud_free_slabs,
+ howmany(keg->uk_reserve - partial, keg->uk_ipers));
+ } else {
+ stokeep = 0;
+ }
+ stofree = dom->ud_free_slabs - stokeep;
+
+ /*
+ * Partition the free slabs into two sets: those that must be kept in
+ * order to maintain the reserve, and those which may be released back
+ * to the system. Since one set may be much larger than the other,
+ * always populate the smaller of the two sets and swap them if
+ * necessary.
+ */
+ for (i = min(stofree, stokeep); i > 0; i--) {
+ slab = LIST_FIRST(&dom->ud_free_slab);
+ LIST_REMOVE(slab, us_link);
+ LIST_INSERT_HEAD(&freeslabs, slab, us_link);
+ }
+ if (stofree > stokeep)
+ LIST_SWAP(&freeslabs, &dom->ud_free_slab, uma_slab, us_link);
+
+ if ((keg->uk_flags & UMA_ZFLAG_HASH) != 0) {
+ LIST_FOREACH(slab, &freeslabs, us_link)
+ UMA_HASH_REMOVE(&keg->uk_hash, slab);
+ }
+ dom->ud_free_items -= stofree * keg->uk_ipers;
+ dom->ud_free_slabs -= stofree;
+ dom->ud_pages -= stofree * keg->uk_ppera;
+ KEG_UNLOCK(keg, domain);
+
+ LIST_FOREACH_SAFE(slab, &freeslabs, us_link, tmp)
+ keg_free_slab(keg, slab, keg->uk_ipers);
+}
+
/*
* Frees pages from a keg back to the system. This is done on demand from
* the pageout daemon.
@@ -1424,35 +1482,12 @@
static void
keg_drain(uma_keg_t keg)
{
- struct slabhead freeslabs;
- uma_domain_t dom;
- uma_slab_t slab, tmp;
- int i, n;
+ int i;
- if (keg->uk_flags & UMA_ZONE_NOFREE || keg->uk_freef == NULL)
+ if ((keg->uk_flags & UMA_ZONE_NOFREE) != 0)
return;
-
- for (i = 0; i < vm_ndomains; i++) {
- CTR4(KTR_UMA, "keg_drain %s(%p) domain %d free items: %u",
- keg->uk_name, keg, i, dom->ud_free_items);
- dom = &keg->uk_domain[i];
- LIST_INIT(&freeslabs);
-
- KEG_LOCK(keg, i);
- if ((keg->uk_flags & UMA_ZFLAG_HASH) != 0) {
- LIST_FOREACH(slab, &dom->ud_free_slab, us_link)
- UMA_HASH_REMOVE(&keg->uk_hash, slab);
- }
- n = dom->ud_free_slabs;
- LIST_SWAP(&freeslabs, &dom->ud_free_slab, uma_slab, us_link);
- dom->ud_free_slabs = 0;
- dom->ud_free_items -= n * keg->uk_ipers;
- dom->ud_pages -= n * keg->uk_ppera;
- KEG_UNLOCK(keg, i);
-
- LIST_FOREACH_SAFE(slab, &freeslabs, us_link, tmp)
- keg_free_slab(keg, slab, keg->uk_ipers);
- }
+ for (i = 0; i < vm_ndomains; i++)
+ keg_drain_domain(keg, i);
}
static void
@@ -2411,6 +2446,9 @@
SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
"align", CTLFLAG_RD, &keg->uk_align, 0,
"item alignment mask");
+ SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
+ "reserve", CTLFLAG_RD, &keg->uk_reserve, 0,
+ "number of reserved items");
SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
"efficiency", CTLFLAG_RD | CTLTYPE_INT | CTLFLAG_MPSAFE,
keg, 0, sysctl_handle_uma_slab_efficiency, "I",

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