Applied, thanks!
Sergey Bugaev, le lun. 26 juin 2023 14:26:52 +0300, a ecrit:
> Previously, vm_object_coalesce would only succeed with next_object being
> VM_OBJECT_NULL (and with the previous patch, with the two object
> references pointing to the same object). This patch additionally allows
> the inverse: prev_object being VM_OBJECT_NULL and next_object being some
> internal VM object that we have not created a pager port for, provided
> the offset of the existing mapping in the object allows for placing the
> new mapping before it.
>
> This is not used anywhere at the moment (the only caller, vm_map_enter,
> ensures that next_object is either VM_OBJECT_NULL or an object that has
> a pager port), but it will get used with the next patch.
> ---
> vm/vm_object.c | 75 +++++++++++++++++++++++++++++++++-----------------
> 1 file changed, 49 insertions(+), 26 deletions(-)
>
> diff --git a/vm/vm_object.c b/vm/vm_object.c
> index b00e90d2..e01c1856 100644
> --- a/vm/vm_object.c
> +++ b/vm/vm_object.c
> @@ -2692,7 +2692,7 @@ void vm_object_page_remove(
> *
> * returns TRUE if objects were combined.
> *
> - * NOTE: Only works at the moment if the second object is NULL -
> + * NOTE: Only works at the moment if one of the objects is NULL
> * or if the objects are the same - otherwise, which
> * object do we lock first?
> *
> @@ -2717,6 +2717,7 @@ boolean_t vm_object_coalesce(
> vm_size_t prev_size,
> vm_size_t next_size)
> {
> + vm_object_t object;
> vm_size_t newsize;
>
> if (prev_object == next_object) {
> @@ -2735,19 +2736,24 @@ boolean_t vm_object_coalesce(
> * Don't know how to merge two different
> * objects yet.
> */
> - return FALSE;
> + if (prev_object != VM_OBJECT_NULL)
> + return FALSE;
> +
> + object = next_object;
> + } else {
> + object = prev_object;
> }
>
> - vm_object_lock(prev_object);
> + vm_object_lock(object);
>
> /*
> * Try to collapse the object first
> */
> - vm_object_collapse(prev_object);
> + vm_object_collapse(object);
>
> /*
> * Can't coalesce if pages not mapped to
> - * prev_entry may be in use anyway:
> + * the object may be in use anyway:
> * . more than one reference
> * . paged out
> * . shadows another object
> @@ -2755,33 +2761,50 @@ boolean_t vm_object_coalesce(
> * . paging references (pages might be in page-list)
> */
>
> - if ((prev_object->ref_count > 1) ||
> - prev_object->pager_created ||
> - prev_object->used_for_pageout ||
> - (prev_object->shadow != VM_OBJECT_NULL) ||
> - (prev_object->copy != VM_OBJECT_NULL) ||
> - (prev_object->paging_in_progress != 0)) {
> - vm_object_unlock(prev_object);
> + if ((object->ref_count > 1) ||
> + object->pager_created ||
> + object->used_for_pageout ||
> + (object->shadow != VM_OBJECT_NULL) ||
> + (object->copy != VM_OBJECT_NULL) ||
> + (object->paging_in_progress != 0)) {
> + vm_object_unlock(object);
> return FALSE;
> }
>
> - /*
> - * Remove any pages that may still be in the object from
> - * a previous deallocation.
> - */
> -
> - vm_object_page_remove(prev_object,
> + if (object == prev_object) {
> + /*
> + * Remove any pages that may still be in
> + * the object from a previous deallocation.
> + */
> + vm_object_page_remove(object,
> prev_offset + prev_size,
> prev_offset + prev_size + next_size);
> + /*
> + * Extend the object if necessary.
> + */
> + newsize = prev_offset + prev_size + next_size;
> + if (newsize > object->size)
> + object->size = newsize;
> + } else {
> + /*
> + * Check if we have enough space in the object
> + * offset space to insert the new mapping before
> + * the existing one.
> + */
> + if (next_offset < prev_size) {
> + vm_object_unlock(object);
> + return FALSE;
> + }
> + /*
> + * Remove any pages that may still be in
> + * the object from a previous deallocation.
> + */
> + vm_object_page_remove(object,
> + next_offset - prev_size,
> + next_offset);
> + }
>
> - /*
> - * Extend the object if necessary.
> - */
> - newsize = prev_offset + prev_size + next_size;
> - if (newsize > prev_object->size)
> - prev_object->size = newsize;
> -
> - vm_object_unlock(prev_object);
> + vm_object_unlock(object);
> return TRUE;
> }
>
> --
> 2.41.0
>
--
Samuel
---
Pour une évaluation indépendante, transparente et rigoureuse !
Je soutiens la Commission d'Évaluation de l'Inria.
