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Optimize vm_page_try_to_free(). Specifically, the call to pmap_remove_all()

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can be avoided when the page's containing object has a reference count of
zero.  (If the object has a reference count of zero, then none of its pages
can possibly be mapped.)

Address nearby style issues in vm_page_try_to_free(), and change its
return type to "bool".

Reviewed by:	kib, markj
MFC after:	1 week
This commit is contained in:
Alan Cox 2017-09-24 16:50:10 +00:00
parent 7ed082c4bb
commit 494c6e43d3
2 changed files with 12 additions and 10 deletions
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20
sys/vm/vm_page.c
View File

@ -3081,23 +3081,25 @@ vm_page_unswappable(vm_page_t m)
* vm_page_try_to_free()
*
* Attempt to free the page. If we cannot free it, we do nothing.
* 1 is returned on success, 0 on failure.
* true is returned on success, false on failure.
*/
int
bool
vm_page_try_to_free(vm_page_t m)
{
vm_page_lock_assert(m, MA_OWNED);
vm_page_assert_locked(m);
if (m->object != NULL)
VM_OBJECT_ASSERT_WLOCKED(m->object);
if (m->dirty || m->hold_count || m->wire_count ||
if (m->dirty != 0 || m->hold_count != 0 || m->wire_count != 0 ||
(m->oflags & VPO_UNMANAGED) != 0 || vm_page_busied(m))
return (0);
pmap_remove_all(m);
if (m->dirty)
return (0);
return (false);
if (m->object != NULL && m->object->ref_count != 0) {
pmap_remove_all(m);
if (m->dirty != 0)
return (false);
}
vm_page_free(m);
return (1);
return (true);
}
/*

2
sys/vm/vm_page.h
View File

@ -477,7 +477,6 @@ void vm_page_change_lock(vm_page_t m, struct mtx **mtx);
vm_page_t vm_page_grab (vm_object_t, vm_pindex_t, int);
int vm_page_grab_pages(vm_object_t object, vm_pindex_t pindex, int allocflags,
vm_page_t *ma, int count);
int vm_page_try_to_free (vm_page_t);
void vm_page_deactivate (vm_page_t);
void vm_page_deactivate_noreuse(vm_page_t);
void vm_page_dequeue(vm_page_t m);
@ -513,6 +512,7 @@ void vm_page_set_valid_range(vm_page_t m, int base, int size);
int vm_page_sleep_if_busy(vm_page_t m, const char *msg);
vm_offset_t vm_page_startup(vm_offset_t vaddr);
void vm_page_sunbusy(vm_page_t m);
bool vm_page_try_to_free(vm_page_t m);
int vm_page_trysbusy(vm_page_t m);
void vm_page_unhold_pages(vm_page_t *ma, int count);
void vm_page_unswappable(vm_page_t m);