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Code Issues Releases Activity

Push down the responsibility for zeroing a physical page from the

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caller to vm_page_grab().  Although this gives VM_ALLOC_ZERO a
different meaning for vm_page_grab() than for vm_page_alloc(), I feel
such change is necessary to accomplish other goals.  Specifically, I
want to make the PG_ZERO flag immutable between the time it is
allocated by vm_page_alloc() and freed by vm_page_free() or
vm_page_free_zero() to avoid locking overheads.  Once we gave up on
the ability to automatically recognize a zeroed page upon entry to
vm_page_free(), the ability to mutate the PG_ZERO flag became useless.
Instead, I would like to say that "Once a page becomes valid, its
PG_ZERO flag must be ignored."
This commit is contained in:
Alan Cox 2004-04-24 20:53:55 +00:00
parent 63224f60c3
commit 7ef6ba5d27
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=128613
7 changed files with 2 additions and 13 deletions
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3
sys/alpha/alpha/pmap.c
View File

@ -1194,8 +1194,6 @@ _pmap_allocpte(pmap, ptepindex)
VM_OBJECT_LOCK(pmap->pm_pteobj);
m = vm_page_grab(pmap->pm_pteobj, ptepindex,
VM_ALLOC_WIRED | VM_ALLOC_ZERO | VM_ALLOC_RETRY);
if ((m->flags & PG_ZERO) == 0)
pmap_zero_page(m);
KASSERT(m->queue == PQ_NONE,
("_pmap_allocpte: %p->queue != PQ_NONE", m));
@ -1242,7 +1240,6 @@ _pmap_allocpte(pmap, ptepindex)
vm_page_lock_queues();
m->valid = VM_PAGE_BITS_ALL;
vm_page_flag_clear(m, PG_ZERO);
vm_page_wakeup(m);
vm_page_unlock_queues();
if (!is_object_locked)

2
sys/dev/agp/agp.c
View File

@ -524,8 +524,6 @@ agp_generic_bind_memory(device_t dev, struct agp_memory *mem,
m = vm_page_grab(mem->am_obj, OFF_TO_IDX(i),
VM_ALLOC_WIRED | VM_ALLOC_ZERO | VM_ALLOC_RETRY);
VM_OBJECT_UNLOCK(mem->am_obj);
if ((m->flags & PG_ZERO) == 0)
pmap_zero_page(m);
AGP_DPF("found page pa=%#x\n", VM_PAGE_TO_PHYS(m));
/*

2
sys/dev/agp/agp_i810.c
View File

@ -612,8 +612,6 @@ agp_i810_alloc_memory(device_t dev, int type, vm_size_t size)
m = vm_page_grab(mem->am_obj, 0,
VM_ALLOC_WIRED | VM_ALLOC_ZERO | VM_ALLOC_RETRY);
VM_OBJECT_UNLOCK(mem->am_obj);
if ((m->flags & PG_ZERO) == 0)
pmap_zero_page(m);
vm_page_lock_queues();
mem->am_physical = VM_PAGE_TO_PHYS(m);
vm_page_wakeup(m);

2
sys/pci/agp.c
View File

@ -524,8 +524,6 @@ agp_generic_bind_memory(device_t dev, struct agp_memory *mem,
m = vm_page_grab(mem->am_obj, OFF_TO_IDX(i),
VM_ALLOC_WIRED | VM_ALLOC_ZERO | VM_ALLOC_RETRY);
VM_OBJECT_UNLOCK(mem->am_obj);
if ((m->flags & PG_ZERO) == 0)
pmap_zero_page(m);
AGP_DPF("found page pa=%#x\n", VM_PAGE_TO_PHYS(m));
/*

2
sys/pci/agp_i810.c
View File

@ -612,8 +612,6 @@ agp_i810_alloc_memory(device_t dev, int type, vm_size_t size)
m = vm_page_grab(mem->am_obj, 0,
VM_ALLOC_WIRED | VM_ALLOC_ZERO | VM_ALLOC_RETRY);
VM_OBJECT_UNLOCK(mem->am_obj);
if ((m->flags & PG_ZERO) == 0)
pmap_zero_page(m);
vm_page_lock_queues();
mem->am_physical = VM_PAGE_TO_PHYS(m);
vm_page_wakeup(m);

2
sys/vm/vm_kern.c
View File

@ -198,8 +198,6 @@ kmem_alloc(map, size)
mem = vm_page_grab(kernel_object, OFF_TO_IDX(offset + i),
VM_ALLOC_ZERO | VM_ALLOC_RETRY);
if ((mem->flags & PG_ZERO) == 0)
pmap_zero_page(mem);
mem->valid = VM_PAGE_BITS_ALL;
vm_page_lock_queues();
vm_page_unmanage(mem);

2
sys/vm/vm_page.c
View File

@ -1460,6 +1460,8 @@ vm_page_grab(vm_object_t object, vm_pindex_t pindex, int allocflags)
return NULL;
goto retrylookup;
}
if (allocflags & VM_ALLOC_ZERO && (m->flags & PG_ZERO) == 0)
pmap_zero_page(m);
return m;
}