Avoid page lookups in the top-level object in vm_object_madvise().
We can iterate over consecutive resident pages in the top-level object using the object's page list rather than by performing lookups in the object radix tree. This extends one of the optimizations in r312208 to the case where a shadow chain is present. Suggested by: alc Reviewed by: alc, kib (previous version) MFC after: 2 weeks Differential Revision: https://reviews.freebsd.org/D9282
This commit is contained in:
Mark Johnston
parent
fab7084f12
commit
aa3650ea36
@ -1074,6 +1074,33 @@ vm_object_sync(vm_object_t object, vm_ooffset_t offset, vm_size_t size,
|
||||
return (res);
|
||||
}
|
||||
|
||||
/*
|
||||
* Determine whether the given advice can be applied to the object. Advice is
|
||||
* not applied to unmanaged pages since they never belong to page queues, and
|
||||
* since MADV_FREE is destructive, it can apply only to anonymous pages that
|
||||
* have been mapped at most once.
|
||||
*/
|
||||
static bool
|
||||
vm_object_advice_applies(vm_object_t object, int advice)
|
||||
{
|
||||
|
||||
if ((object->flags & OBJ_UNMANAGED) != 0)
|
||||
return (false);
|
||||
if (advice != MADV_FREE)
|
||||
return (true);
|
||||
return ((object->type == OBJT_DEFAULT || object->type == OBJT_SWAP) &&
|
||||
(object->flags & OBJ_ONEMAPPING) != 0);
|
||||
}
|
||||
|
||||
static void
|
||||
vm_object_madvise_freespace(vm_object_t object, int advice, vm_pindex_t pindex,
|
||||
vm_size_t size)
|
||||
{
|
||||
|
||||
if (advice == MADV_FREE && object->type == OBJT_SWAP)
|
||||
swap_pager_freespace(object, pindex, size);
|
||||
}
|
||||
|
||||
/*
|
||||
* vm_object_madvise:
|
||||
*
|
||||
@ -1101,100 +1128,102 @@ vm_object_madvise(vm_object_t object, vm_pindex_t pindex, vm_pindex_t end,
|
||||
{
|
||||
vm_pindex_t tpindex;
|
||||
vm_object_t backing_object, tobject;
|
||||
vm_page_t m;
|
||||
vm_page_t m, tm;
|
||||
|
||||
if (object == NULL)
|
||||
return;
|
||||
|
||||
VM_OBJECT_WLOCK(object);
|
||||
for (m = NULL; pindex < end; pindex++) {
|
||||
relookup:
|
||||
VM_OBJECT_WLOCK(object);
|
||||
if (!vm_object_advice_applies(object, advice)) {
|
||||
VM_OBJECT_WUNLOCK(object);
|
||||
return;
|
||||
}
|
||||
for (m = vm_page_find_least(object, pindex); pindex < end; pindex++) {
|
||||
tobject = object;
|
||||
tpindex = pindex;
|
||||
shadowlookup:
|
||||
/*
|
||||
* MADV_FREE only operates on OBJT_DEFAULT or OBJT_SWAP pages
|
||||
* and those pages must be OBJ_ONEMAPPING.
|
||||
*/
|
||||
if (advice == MADV_FREE) {
|
||||
if ((tobject->type != OBJT_DEFAULT &&
|
||||
tobject->type != OBJT_SWAP) ||
|
||||
(tobject->flags & OBJ_ONEMAPPING) == 0) {
|
||||
goto unlock_tobject;
|
||||
}
|
||||
} else if ((tobject->flags & OBJ_UNMANAGED) != 0)
|
||||
goto unlock_tobject;
|
||||
|
||||
/*
|
||||
* In the common case where the object has no backing object, we
|
||||
* can avoid performing lookups at each pindex. In either case,
|
||||
* when applying MADV_FREE we take care to release any swap
|
||||
* space used to store non-resident pages.
|
||||
* If the next page isn't resident in the top-level object, we
|
||||
* need to search the shadow chain. When applying MADV_FREE, we
|
||||
* take care to release any swap space used to store
|
||||
* non-resident pages.
|
||||
*/
|
||||
if (object->backing_object == NULL) {
|
||||
m = (m != NULL) ? TAILQ_NEXT(m, listq) :
|
||||
vm_page_find_least(object, pindex);
|
||||
tpindex = (m != NULL && m->pindex < end) ?
|
||||
m->pindex : end;
|
||||
if (advice == MADV_FREE && object->type == OBJT_SWAP &&
|
||||
tpindex > pindex)
|
||||
swap_pager_freespace(object, pindex,
|
||||
tpindex - pindex);
|
||||
if ((pindex = tpindex) == end)
|
||||
break;
|
||||
} else if ((m = vm_page_lookup(tobject, tpindex)) == NULL) {
|
||||
if (advice == MADV_FREE && tobject->type == OBJT_SWAP)
|
||||
swap_pager_freespace(tobject, tpindex, 1);
|
||||
if (m == NULL || pindex < m->pindex) {
|
||||
/*
|
||||
* Prepare to search the next object in the chain.
|
||||
* Optimize a common case: if the top-level object has
|
||||
* no backing object, we can skip over the non-resident
|
||||
* range in constant time.
|
||||
*/
|
||||
backing_object = tobject->backing_object;
|
||||
if (backing_object == NULL)
|
||||
goto unlock_tobject;
|
||||
VM_OBJECT_WLOCK(backing_object);
|
||||
tpindex += OFF_TO_IDX(tobject->backing_object_offset);
|
||||
if (tobject != object)
|
||||
VM_OBJECT_WUNLOCK(tobject);
|
||||
tobject = backing_object;
|
||||
goto shadowlookup;
|
||||
if (object->backing_object == NULL) {
|
||||
tpindex = (m != NULL && m->pindex < end) ?
|
||||
m->pindex : end;
|
||||
vm_object_madvise_freespace(object, advice,
|
||||
pindex, tpindex - pindex);
|
||||
if ((pindex = tpindex) == end)
|
||||
break;
|
||||
goto next_page;
|
||||
}
|
||||
|
||||
tpindex = pindex;
|
||||
do {
|
||||
vm_object_madvise_freespace(tobject, advice,
|
||||
tpindex, 1);
|
||||
/*
|
||||
* Prepare to search the next object in the
|
||||
* chain.
|
||||
*/
|
||||
backing_object = tobject->backing_object;
|
||||
if (backing_object == NULL)
|
||||
goto next_pindex;
|
||||
VM_OBJECT_WLOCK(backing_object);
|
||||
tpindex +=
|
||||
OFF_TO_IDX(tobject->backing_object_offset);
|
||||
if (tobject != object)
|
||||
VM_OBJECT_WUNLOCK(tobject);
|
||||
tobject = backing_object;
|
||||
if (!vm_object_advice_applies(tobject, advice))
|
||||
goto next_pindex;
|
||||
} while ((tm = vm_page_lookup(tobject, tpindex)) ==
|
||||
NULL);
|
||||
} else {
|
||||
next_page:
|
||||
tm = m;
|
||||
m = TAILQ_NEXT(m, listq);
|
||||
}
|
||||
|
||||
/*
|
||||
* If the page is not in a normal state, skip it.
|
||||
*/
|
||||
if (m->valid != VM_PAGE_BITS_ALL)
|
||||
goto unlock_tobject;
|
||||
vm_page_lock(m);
|
||||
if (m->hold_count != 0 || m->wire_count != 0) {
|
||||
vm_page_unlock(m);
|
||||
goto unlock_tobject;
|
||||
if (tm->valid != VM_PAGE_BITS_ALL)
|
||||
goto next_pindex;
|
||||
vm_page_lock(tm);
|
||||
if (tm->hold_count != 0 || tm->wire_count != 0) {
|
||||
vm_page_unlock(tm);
|
||||
goto next_pindex;
|
||||
}
|
||||
KASSERT((m->flags & PG_FICTITIOUS) == 0,
|
||||
("vm_object_madvise: page %p is fictitious", m));
|
||||
KASSERT((m->oflags & VPO_UNMANAGED) == 0,
|
||||
("vm_object_madvise: page %p is not managed", m));
|
||||
if (vm_page_busied(m)) {
|
||||
KASSERT((tm->flags & PG_FICTITIOUS) == 0,
|
||||
("vm_object_madvise: page %p is fictitious", tm));
|
||||
KASSERT((tm->oflags & VPO_UNMANAGED) == 0,
|
||||
("vm_object_madvise: page %p is not managed", tm));
|
||||
if (vm_page_busied(tm)) {
|
||||
if (object != tobject)
|
||||
VM_OBJECT_WUNLOCK(tobject);
|
||||
VM_OBJECT_WUNLOCK(object);
|
||||
if (advice == MADV_WILLNEED) {
|
||||
/*
|
||||
* Reference the page before unlocking and
|
||||
* sleeping so that the page daemon is less
|
||||
* likely to reclaim it.
|
||||
* likely to reclaim it.
|
||||
*/
|
||||
vm_page_aflag_set(m, PGA_REFERENCED);
|
||||
vm_page_aflag_set(tm, PGA_REFERENCED);
|
||||
}
|
||||
if (object != tobject)
|
||||
VM_OBJECT_WUNLOCK(object);
|
||||
VM_OBJECT_WUNLOCK(tobject);
|
||||
vm_page_busy_sleep(m, "madvpo", false);
|
||||
m = NULL;
|
||||
VM_OBJECT_WLOCK(object);
|
||||
vm_page_busy_sleep(tm, "madvpo", false);
|
||||
goto relookup;
|
||||
}
|
||||
vm_page_advise(m, advice);
|
||||
vm_page_unlock(m);
|
||||
if (advice == MADV_FREE && tobject->type == OBJT_SWAP)
|
||||
swap_pager_freespace(tobject, tpindex, 1);
|
||||
unlock_tobject:
|
||||
vm_page_advise(tm, advice);
|
||||
vm_page_unlock(tm);
|
||||
vm_object_madvise_freespace(tobject, advice, tm->pindex, 1);
|
||||
next_pindex:
|
||||
if (tobject != object)
|
||||
VM_OBJECT_WUNLOCK(tobject);
|
||||
}
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user