less waste for amaps in the common case:

allocate a single malloc chunk instead of three and allocate a single
slot for a single page instead of four slots. ok miod@ tedu@ @deraadt

1 files changed, 17 insertions, 36 deletions

diff --git a/sys/uvm/uvm_amap.c b/sys/uvm/uvm_amap.c
index 81e315831e5..c939baf29cf 100644
--- a/sys/uvm/uvm_amap.c
+++ b/sys/uvm/uvm_amap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_amap.c,v 1.41 2008/08/26 15:39:27 kettenis Exp $	*/
+/*	$OpenBSD: uvm_amap.c,v 1.42 2008/09/12 08:55:41 otto Exp $	*/
 /*	$NetBSD: uvm_amap.c,v 1.27 2000/11/25 06:27:59 chs Exp $	*/
 
 /*
@@ -67,6 +67,8 @@ struct pool uvm_amap_pool;
 
 LIST_HEAD(, vm_amap) amap_list;
 
+#define MALLOC_SLOT_UNIT (2 * sizeof(int) + sizeof(struct vm_anon *))
+
 /*
  * local functions
  */
@@ -190,8 +192,8 @@ amap_alloc1(int slots, int padslots, int waitf)
 	if (amap == NULL)
 		return(NULL);
 
-	totalslots = malloc_roundup((slots + padslots) * sizeof(int)) /
-	    sizeof(int);
+	totalslots = malloc_roundup((slots + padslots) * MALLOC_SLOT_UNIT) /
+	    MALLOC_SLOT_UNIT;
 	amap->am_ref = 1;
 	amap->am_flags = 0;
 #ifdef UVM_AMAP_PPREF
@@ -201,26 +203,18 @@ amap_alloc1(int slots, int padslots, int waitf)
 	amap->am_nslot = slots;
 	amap->am_nused = 0;
 
-	amap->am_slots = malloc(totalslots * sizeof(int), M_UVMAMAP,
+	amap->am_slots = malloc(totalslots * MALLOC_SLOT_UNIT, M_UVMAMAP,
 	    waitf);
 	if (amap->am_slots == NULL)
 		goto fail1;
 
-	amap->am_bckptr = malloc(totalslots * sizeof(int), M_UVMAMAP, waitf);
-	if (amap->am_bckptr == NULL)
-		goto fail2;
-
-	amap->am_anon = malloc(totalslots * sizeof(struct vm_anon *),
-	    M_UVMAMAP, waitf);
-	if (amap->am_anon == NULL)
-		goto fail3;
+	amap->am_bckptr = (int *)(((char *)amap->am_slots) + totalslots *
+	    sizeof(int));
+	amap->am_anon = (struct vm_anon **)(((char *)amap->am_bckptr) +
+	    totalslots * sizeof(int));
 
 	return(amap);
 
-fail3:
-	free(amap->am_bckptr, M_UVMAMAP);
-fail2:
-	free(amap->am_slots, M_UVMAMAP);
 fail1:
 	pool_put(&uvm_amap_pool, amap);
 	return (NULL);
@@ -271,8 +265,6 @@ amap_free(struct vm_amap *amap)
 	KASSERT((amap->am_flags & AMAP_SWAPOFF) == 0);
 
 	free(amap->am_slots, M_UVMAMAP);
-	free(amap->am_bckptr, M_UVMAMAP);
-	free(amap->am_anon, M_UVMAMAP);
 #ifdef UVM_AMAP_PPREF
 	if (amap->am_ppref && amap->am_ppref != PPREF_NONE)
 		free(amap->am_ppref, M_UVMAMAP);
@@ -369,7 +361,8 @@ amap_extend(struct vm_map_entry *entry, vsize_t addsize)
 	 * XXXCDC: could we take advantage of a kernel realloc()?  
 	 */
 
-	slotalloc = malloc_roundup(slotneed * sizeof(int)) / sizeof(int);
+	slotalloc = malloc_roundup(slotneed * MALLOC_SLOT_UNIT) /
+	    MALLOC_SLOT_UNIT;
 #ifdef UVM_AMAP_PPREF
 	newppref = NULL;
 	if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
@@ -382,22 +375,9 @@ amap_extend(struct vm_map_entry *entry, vsize_t addsize)
 		}
 	}
 #endif
-	newsl = malloc(slotalloc * sizeof(int), M_UVMAMAP,
-	    M_WAITOK | M_CANFAIL);
-	newbck = malloc(slotalloc * sizeof(int), M_UVMAMAP,
+	newsl = malloc(slotalloc * MALLOC_SLOT_UNIT, M_UVMAMAP,
 	    M_WAITOK | M_CANFAIL);
-	newover = malloc(slotalloc * sizeof(struct vm_anon *), M_UVMAMAP,
-	    M_WAITOK | M_CANFAIL);
-	if (newsl == NULL || newbck == NULL || newover == NULL) {
-		if (newsl != NULL) {
-			free(newsl, M_UVMAMAP);
-		}
-		if (newbck != NULL) {
-			free(newbck, M_UVMAMAP);
-		}
-		if (newover != NULL) {
-			free(newover, M_UVMAMAP);
-		}
+	if (newsl == NULL) {
 #ifdef UVM_AMAP_PPREF
 		if (newppref != NULL) {
 			free(newppref, M_UVMAMAP);
@@ -405,6 +385,9 @@ amap_extend(struct vm_map_entry *entry, vsize_t addsize)
 #endif
 		return (ENOMEM);
 	}
+	newbck = (int *)(((char *)newsl) + slotalloc * sizeof(int));
+	newover = (struct vm_anon **)(((char *)newbck) + slotalloc *
+	    sizeof(int));
 	KASSERT(amap->am_maxslot < slotneed);
 
 	/*
@@ -452,8 +435,6 @@ amap_extend(struct vm_map_entry *entry, vsize_t addsize)
 
 	/* and free */
 	free(oldsl, M_UVMAMAP);
-	free(oldbck, M_UVMAMAP);
-	free(oldover, M_UVMAMAP);
 #ifdef UVM_AMAP_PPREF
 	if (oldppref && oldppref != PPREF_NONE)
 		free(oldppref, M_UVMAMAP);