Applied, thanks!
Sergey Bugaev, le lun. 26 juin 2023 14:26:54 +0300, a ecrit:
> If a deallocated VM map entry refers to an object that only has a single
> reference and doesn't have a pager port, we can eagerly release any
> physical pages that were contained in the deallocated range.
>
> This is not a 100% solution: it is still possible to "leak" physical
> pages that can never appear in virtual memory again by creating several
> references to a memory object (perhaps by forking a VM map with
> VM_INHERIT_SHARE) and deallocating the pages from all the maps referring
> to the object. That being said, it should help to release the pages in
> the common case sooner.
> ---
>
> This is also probably fine to do if object->temporary, but let's stick
> with !object->pager_created as a more conservative check.
>
> vm/vm_map.c | 26 +++++++++++++++++++++-----
> 1 file changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/vm/vm_map.c b/vm/vm_map.c
> index 0d3b11f2..97fc09ce 100644
> --- a/vm/vm_map.c
> +++ b/vm/vm_map.c
> @@ -1902,11 +1902,13 @@ void vm_map_entry_delete(
> vm_map_entry_t entry)
> {
> vm_offset_t s, e;
> + vm_size_t size;
> vm_object_t object;
> extern vm_object_t kernel_object;
>
> s = entry->vme_start;
> e = entry->vme_end;
> + size = e - s;
>
> /*Check if projected buffer*/
> if (map != kernel_map && entry->projected_on != 0) {
> @@ -1945,15 +1947,29 @@ void vm_map_entry_delete(
> if (object == kernel_object) {
> vm_object_lock(object);
> vm_object_page_remove(object, entry->offset,
> - entry->offset + (e - s));
> + entry->offset + size);
> vm_object_unlock(object);
> } else if (entry->is_shared) {
> vm_object_pmap_remove(object,
> entry->offset,
> - entry->offset + (e - s));
> - }
> - else {
> + entry->offset + size);
> + } else {
> pmap_remove(map->pmap, s, e);
> + /*
> + * If this object has no pager and our
> + * reference to the object is the only
> + * one, we can release the deleted pages
> + * now.
> + */
> + vm_object_lock(object);
> + if ((!object->pager_created) &&
> + (object->ref_count == 1) &&
> + (object->paging_in_progress == 0)) {
> + vm_object_page_remove(object,
> + entry->offset,
> + entry->offset + size);
> + }
> + vm_object_unlock(object);
> }
> }
>
> @@ -1968,7 +1984,7 @@ void vm_map_entry_delete(
> vm_object_deallocate(entry->object.vm_object);
>
> vm_map_entry_unlink(map, entry);
> - map->size -= e - s;
> + map->size -= size;
>
> vm_map_entry_dispose(map, entry);
> }
> --
> 2.41.0
>
--
Samuel
---
Pour une évaluation indépendante, transparente et rigoureuse !
Je soutiens la Commission d'Évaluation de l'Inria.
