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Allow vm object coalescing to occur in the midst of a vm object when the

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OBJ_ONEMAPPING flag is set.  In other words, allow recycling of existing
but unused subranges of a vm object when the OBJ_ONEMAPPING flag is set.

Such situations are increasingly common with jemalloc >= 5.0.  This
change has the expected effect of reducing the number of vm map entry and
object allocations and increasing the number of superpage promotions.

Reviewed by:	kib, markj
Tested by:	pho
MFC after:	6 weeks
Differential Revision:	https://reviews.freebsd.org/D16501
This commit is contained in:
alc 2018-07-31 17:41:48 +00:00
parent 04eea1d6e8
commit e331f32ea2
1 changed files with 3 additions and 2 deletions
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5
sys/vm/vm_object.c
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@ -2142,8 +2142,9 @@ vm_object_coalesce(vm_object_t prev_object, vm_ooffset_t prev_offset,
next_size >>= PAGE_SHIFT;
next_pindex = OFF_TO_IDX(prev_offset) + prev_size;
if ((prev_object->ref_count > 1) &&
(prev_object->size != next_pindex)) {
if (prev_object->ref_count > 1 &&
prev_object->size != next_pindex &&
(prev_object->flags & OBJ_ONEMAPPING) == 0) {
VM_OBJECT_WUNLOCK(prev_object);
return (FALSE);
}