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More progress on VMA merge/shadow collapse.

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Done the merging, but deleting pages from different pagers is the
current issue.
This commit is contained in:
Bahadir Balban
2008-03-10 18:38:08 +00:00
parent 584815a4db
commit 47a6a31249
5 changed files with 133 additions and 108 deletions
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130
tasks/mm0/src/fault.c
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@@ -18,12 +18,6 @@
#include <shm.h>
#include <file.h>
/* FIXME: FIXME: FIXME: FIXME: FIXME: FIXME: FIXME: FIXME: TODO:
* For every page that is allocated, (read-only file pages) and anon pages
* etc. Page cache for that page's file must be visited first, before
* allocation.
*/
unsigned long fault_to_file_offset(struct fault_data *fault)
{
/* Fault's offset in its vma */
@@ -122,6 +116,93 @@ int vma_drop_link(struct vm_obj_link *shadower,
list_del(&shadower->shref);
}
/*
* Checks if page cache pages of lesser is a subset of those of copier.
* Note this just checks the page cache, so if any objects have pages
* swapped to disk, this function does not rule.
*/
int vm_object_check_subset(struct vm_object *copier,
struct vm_object *lesser)
{
struct page *pc, *pl;
/* Copier must have equal or more pages to overlap lesser */
if (copier->npages < lesser->npages)
return 1;
/*
* Do a page by page comparison. Every lesser page
* must be in copier for overlap.
*/
list_for_each_entry(pl, &lesser->page_cache, list)
if (!(pc = find_page(copier, pl->offset)))
return 1;
/*
* For all pages of lesser vmo, there seems to be a page
* in the copier vmo. So lesser is a subset of copier
*/
return 0;
}
/* Merges link 1 to link 2 */
int do_vma_merge_link(struct vm_obj_link *link1, struct vm_obj_link *link2)
{
struct vm_object *obj1 = link1->obj;
struct vm_object *obj2 = link2->obj;
struct page *p1, *p2;
/*
* Move all non-intersecting pages to link2. Free all
* intersecting pages.
*/
list_for_each_entry(p1, &obj1->page_cache, list) {
/* Page doesn't exist, move it to shadower */
if (!(p2 = find_page(obj2, p1->offset))) {
list_del(&p1->list);
spin_lock(&page->lock);
p1->owner = obj2;
spin_unlock(&page->lock);
insert_page_olist(p1, obj2);
obj2->npages++;
}
}
/* Delete the object along with all its pages. */
vm_object_delete(obj1);
}
/*
* Merges a vma's shadow object with its shadower. Note this
* must be called when merge is decided.
*/
int vma_merge_link(struct vm_obj_link *vmo_link)
{
struct vm_obj_link *sh_link;
/* Check refcount */
BUG_ON(vmo_link->obj->refcnt != 1);
/* Get the last shadower entry */
sh_link = list_entry(&vmo_link->obj->shadowers.next,
struct vm_obj_link, shref);
/* Remove it */
list_del(&sh_link->shref);
/* Check that there really was one shadower left */
BUG_ON(!list_empty(&vmo_link->obj->shadowers));
/* Do the actual merge */
do_vma_merge_link(vmo_link, sh_link);
}
/*
* To merge, the object should use the last shadow
* reference left, but this reference must be changed
* to point at the vm_obj_link rather than the object
* itself, because it's not possible to find the link
* from the object.
*/
struct vm_obj_link *vma_create_shadow(void)
{
@@ -166,34 +247,6 @@ struct page *copy_page(struct page *orig)
return new;
}
/*
* Checks if page cache pages of lesser is a subset of those of copier.
* Note this just checks the page cache, so if any objects have pages
* swapped to disk, this function does not rule.
*/
int vm_object_check_subset(struct vm_object *copier,
struct vm_object *lesser)
{
struct page *pc, *pl;
/* Copier must have equal or more pages to overlap lesser */
if (copier->npages < lesser->npages)
return 1;
/*
* Do a page by page comparison. Every lesser page
* must be in copier for overlap.
*/
list_for_each_entry(pl, &lesser->page_cache, list)
if (!(pc = find_page(copier, pl->offset)))
return 1;
/*
* For all pages of lesser vmo, there seems to be a page
* in the copier vmo. So lesser is a subset of copier
*/
return 0;
}
/* TODO:
* - Why not allocate a swap descriptor in vma_create_shadow() rather than
* a bare vm_object? It will be needed.
@@ -313,16 +366,9 @@ int copy_on_write(struct fault_data *fault)
/* vm object reference down to one? */
if (vmo_link->obj->refcnt == 1) {
BUG(); /* Check that the mergers are both shadows!!! */
/* TODO: Fill this in! Merge with the only reference */
vm_object_merge(vmo_link);
/*
* To merge, the object should use the last shadow
* reference left, but this reference must be changed
* to point at the vm_obj_link rather than the object
* itself, because it's not possible to find the link
* from the object, and only the link matters.
*/
}
}
}