For amaps with only a few slots, allocate the slots via pool(9)

This saves some memory compared to using malloc, because there's
no roundup to the next bucket size. And it reduces kmem pressure
at least for some architectures (e.g. amd64).

Testing by sthen@ and tobiasu@, thanks!

ok sthen@ deraadt@

1 files changed, 57 insertions, 13 deletions

diff --git a/sys/uvm/uvm_amap.c b/sys/uvm/uvm_amap.c
index 4983afa169e..631dc7a61c9 100644
--- a/sys/uvm/uvm_amap.c
+++ b/sys/uvm/uvm_amap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_amap.c,v 1.60 2016/03/06 14:47:07 stefan Exp $	*/
+/*	$OpenBSD: uvm_amap.c,v 1.61 2016/03/15 18:16:21 stefan Exp $	*/
 /*	$NetBSD: uvm_amap.c,v 1.27 2000/11/25 06:27:59 chs Exp $	*/
 
 /*
@@ -52,8 +52,13 @@
 
 struct pool uvm_amap_pool;
 
+/* Pools for amap slots for the most common amap slot sizes */
+struct pool uvm_amap_slot_pools[UVM_AMAP_CHUNK];
+
 LIST_HEAD(, vm_amap) amap_list;
 
+static char amap_slot_pool_names[UVM_AMAP_CHUNK][13];
+
 #define MALLOC_SLOT_UNIT (2 * sizeof(int) + sizeof(struct vm_anon *))
 
 /*
@@ -151,10 +156,20 @@ pp_setreflen(int *ppref, int offset, int ref, int len)
 void
 amap_init(void)
 {
+	int i;
+
 	/* Initialize the vm_amap pool. */
 	pool_init(&uvm_amap_pool, sizeof(struct vm_amap), 0, 0, PR_WAITOK,
 	    "amappl", NULL);
 	pool_sethiwat(&uvm_amap_pool, 4096);
+
+	for (i = 0; i < nitems(uvm_amap_slot_pools); i++) {
+		snprintf(amap_slot_pool_names[i],
+		    sizeof(amap_slot_pool_names[0]), "amapslotpl%d", i + 1);
+		pool_init(&uvm_amap_slot_pools[i], (i + 1) * MALLOC_SLOT_UNIT,
+		    0, 0, PR_WAITOK, amap_slot_pool_names[i], NULL);
+		pool_sethiwat(&uvm_amap_slot_pools[i], 4096);
+	}
 }
 
 /*
@@ -172,8 +187,13 @@ amap_alloc1(int slots, int padslots, int waitf)
 	if (amap == NULL)
 		return(NULL);
 
-	totalslots = malloc_roundup((slots + padslots) * MALLOC_SLOT_UNIT) /
-	    MALLOC_SLOT_UNIT;
+	totalslots = slots + padslots;
+	KASSERT(totalslots > 0);
+
+	if (totalslots > UVM_AMAP_CHUNK)
+		totalslots = malloc_roundup(totalslots * MALLOC_SLOT_UNIT) /
+		    MALLOC_SLOT_UNIT;
+
 	amap->am_ref = 1;
 	amap->am_flags = 0;
 #ifdef UVM_AMAP_PPREF
@@ -183,8 +203,14 @@ amap_alloc1(int slots, int padslots, int waitf)
 	amap->am_nslot = slots;
 	amap->am_nused = 0;
 
-	amap->am_slots = malloc(totalslots * MALLOC_SLOT_UNIT, M_UVMAMAP,
-	    waitf);
+	if (totalslots > UVM_AMAP_CHUNK)
+		amap->am_slots = malloc(totalslots * MALLOC_SLOT_UNIT,
+		    M_UVMAMAP, waitf);
+	else
+		amap->am_slots = pool_get(
+		    &uvm_amap_slot_pools[totalslots - 1],
+		    (waitf == M_WAITOK) ? PR_WAITOK : PR_NOWAIT);
+
 	if (amap->am_slots == NULL)
 		goto fail1;
 
@@ -238,7 +264,12 @@ amap_free(struct vm_amap *amap)
 	KASSERT(amap->am_ref == 0 && amap->am_nused == 0);
 	KASSERT((amap->am_flags & AMAP_SWAPOFF) == 0);
 
-	free(amap->am_slots, M_UVMAMAP, 0);
+	if (amap->am_maxslot > UVM_AMAP_CHUNK)
+		free(amap->am_slots, M_UVMAMAP, 0);
+	else
+		pool_put(&uvm_amap_slot_pools[amap->am_maxslot - 1],
+		    amap->am_slots);
+
 #ifdef UVM_AMAP_PPREF
 	if (amap->am_ppref && amap->am_ppref != PPREF_NONE)
 		free(amap->am_ppref, M_UVMAMAP, 0);
@@ -324,8 +355,12 @@ amap_extend(struct vm_map_entry *entry, vsize_t addsize)
 	if (slotneed >= UVM_AMAP_LARGE)
 		return E2BIG;
 
-	slotalloc = malloc_roundup(slotneed * MALLOC_SLOT_UNIT) /
-	    MALLOC_SLOT_UNIT;
+	if (slotneed > UVM_AMAP_CHUNK)
+		slotalloc = malloc_roundup(slotneed * MALLOC_SLOT_UNIT) /
+		    MALLOC_SLOT_UNIT;
+	else
+		slotalloc = slotneed;
+
 #ifdef UVM_AMAP_PPREF
 	newppref = NULL;
 	if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
@@ -338,8 +373,12 @@ amap_extend(struct vm_map_entry *entry, vsize_t addsize)
 		}
 	}
 #endif
-	newsl = malloc(slotalloc * MALLOC_SLOT_UNIT, M_UVMAMAP,
-	    M_WAITOK | M_CANFAIL);
+	if (slotneed > UVM_AMAP_CHUNK)
+		newsl = malloc(slotalloc * MALLOC_SLOT_UNIT, M_UVMAMAP,
+		    M_WAITOK | M_CANFAIL);
+	else
+		newsl = pool_get(&uvm_amap_slot_pools[slotalloc - 1],
+		    PR_WAITOK | PR_LIMITFAIL);
 	if (newsl == NULL) {
 #ifdef UVM_AMAP_PPREF
 		if (newppref != NULL) {
@@ -389,12 +428,17 @@ amap_extend(struct vm_map_entry *entry, vsize_t addsize)
 	}
 #endif
 
-	/* update master values */
+	/* free */
+	if (amap->am_maxslot > UVM_AMAP_CHUNK)
+		free(oldsl, M_UVMAMAP, 0);
+	else
+		pool_put(&uvm_amap_slot_pools[amap->am_maxslot - 1],
+		    oldsl);
+
+	/* and update master values */
 	amap->am_nslot = slotneed;
 	amap->am_maxslot = slotalloc;
 
-	/* and free */
-	free(oldsl, M_UVMAMAP, 0);
 #ifdef UVM_AMAP_PPREF
 	if (oldppref && oldppref != PPREF_NONE)
 		free(oldppref, M_UVMAMAP, 0);