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Eliminate an unnecessary atomic operation. Articulate the rationale in

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a comment.
This commit is contained in:
Alan Cox 2004-11-06 21:48:45 +00:00
parent 2a44183a72
commit dad740e967
1 changed files with 11 additions and 4 deletions
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15
sys/vm/vm_object.c
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@ -145,7 +145,16 @@ struct vm_object kmem_object_store;
static long object_collapses;
static long object_bypasses;
/*
* next_index determines the page color that is assigned to the next
* allocated object. Accesses to next_index are not synchronized
* because the effects of two or more object allocations using
* next_index simultaneously are inconsequential. At any given time,
* numerous objects have the same page color.
*/
static int next_index;
static uma_zone_t obj_zone;
#define VM_OBJECTS_INIT 256
@ -211,10 +220,8 @@ _vm_object_allocate(objtype_t type, vm_pindex_t size, vm_object_t object)
incr = PQ_L2_SIZE / 3 + PQ_PRIME1;
else
incr = size;
do
object->pg_color = next_index;
while (!atomic_cmpset_int(&next_index, object->pg_color,
(object->pg_color + incr) & PQ_L2_MASK));
object->pg_color = next_index;
next_index = (object->pg_color + incr) & PQ_L2_MASK;
object->handle = NULL;
object->backing_object = NULL;
object->backing_object_offset = (vm_ooffset_t) 0;