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memcg: simple migration handling

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Now, management of "charge" under page migration is done under following
manner. (Assume migrate page contents from oldpage to newpage)

 before
  - "newpage" is charged before migration.
 at success.
  - "oldpage" is uncharged at somewhere(unmap, radix-tree-replace)
 at failure
  - "newpage" is uncharged.
  - "oldpage" is charged if necessary (*1)

But (*1) is not reliable....because of GFP_ATOMIC.

This patch tries to change behavior as following by charge/commit/cancel ops.

 before
  - charge PAGE_SIZE (no target page)
 success
  - commit charge against "newpage".
 failure
  - commit charge against "oldpage".
    (PCG_USED bit works effectively to avoid double-counting)
  - if "oldpage" is obsolete, cancel charge of PAGE_SIZE.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KAMEZAWA Hiroyuki
2009-01-07 18:07:50 -08:00
committed by Linus Torvalds
parent bced0520fe
commit 01b1ae63c2
3 changed files with 73 additions and 96 deletions
Download Patch File Download Diff File Expand all files Collapse all files

108
mm/memcontrol.c
View File

@@ -627,34 +627,6 @@ int mem_cgroup_newpage_charge(struct page *page,
MEM_CGROUP_CHARGE_TYPE_MAPPED, NULL);
}
/*
* same as mem_cgroup_newpage_charge(), now.
* But what we assume is different from newpage, and this is special case.
* treat this in special function. easy for maintenance.
*/
int mem_cgroup_charge_migrate_fixup(struct page *page,
struct mm_struct *mm, gfp_t gfp_mask)
{
if (mem_cgroup_subsys.disabled)
return 0;
if (PageCompound(page))
return 0;
if (page_mapped(page) || (page->mapping && !PageAnon(page)))
return 0;
if (unlikely(!mm))
mm = &init_mm;
return mem_cgroup_charge_common(page, mm, gfp_mask,
MEM_CGROUP_CHARGE_TYPE_MAPPED, NULL);
}
int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
gfp_t gfp_mask)
{
@@ -697,7 +669,6 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
MEM_CGROUP_CHARGE_TYPE_SHMEM, NULL);
}
void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr)
{
struct page_cgroup *pc;
@@ -782,13 +753,13 @@ void mem_cgroup_uncharge_cache_page(struct page *page)
}
/*
* Before starting migration, account against new page.
* Before starting migration, account PAGE_SIZE to mem_cgroup that the old
* page belongs to.
*/
int mem_cgroup_prepare_migration(struct page *page, struct page *newpage)
int mem_cgroup_prepare_migration(struct page *page, struct mem_cgroup **ptr)
{
struct page_cgroup *pc;
struct mem_cgroup *mem = NULL;
enum charge_type ctype = MEM_CGROUP_CHARGE_TYPE_MAPPED;
int ret = 0;
if (mem_cgroup_subsys.disabled)
@@ -799,42 +770,67 @@ int mem_cgroup_prepare_migration(struct page *page, struct page *newpage)
if (PageCgroupUsed(pc)) {
mem = pc->mem_cgroup;
css_get(&mem->css);
if (PageCgroupCache(pc)) {
if (page_is_file_cache(page))
ctype = MEM_CGROUP_CHARGE_TYPE_CACHE;
else
ctype = MEM_CGROUP_CHARGE_TYPE_SHMEM;
}
}
unlock_page_cgroup(pc);
if (mem) {
ret = mem_cgroup_charge_common(newpage, NULL,
GFP_HIGHUSER_MOVABLE,
ctype, mem);
ret = mem_cgroup_try_charge(NULL, GFP_HIGHUSER_MOVABLE, &mem);
css_put(&mem->css);
}
*ptr = mem;
return ret;
}
/* remove redundant charge if migration failed*/
void mem_cgroup_end_migration(struct page *newpage)
void mem_cgroup_end_migration(struct mem_cgroup *mem,
struct page *oldpage, struct page *newpage)
{
struct page *target, *unused;
struct page_cgroup *pc;
enum charge_type ctype;
if (!mem)
return;
/* at migration success, oldpage->mapping is NULL. */
if (oldpage->mapping) {
target = oldpage;
unused = NULL;
} else {
target = newpage;
unused = oldpage;
}
if (PageAnon(target))
ctype = MEM_CGROUP_CHARGE_TYPE_MAPPED;
else if (page_is_file_cache(target))
ctype = MEM_CGROUP_CHARGE_TYPE_CACHE;
else
ctype = MEM_CGROUP_CHARGE_TYPE_SHMEM;
/* unused page is not on radix-tree now. */
if (unused && ctype != MEM_CGROUP_CHARGE_TYPE_MAPPED)
__mem_cgroup_uncharge_common(unused, ctype);
pc = lookup_page_cgroup(target);
/*
* At success, page->mapping is not NULL.
* special rollback care is necessary when
* 1. at migration failure. (newpage->mapping is cleared in this case)
* 2. the newpage was moved but not remapped again because the task
* exits and the newpage is obsolete. In this case, the new page
* may be a swapcache. So, we just call mem_cgroup_uncharge_page()
* always for avoiding mess. The page_cgroup will be removed if
* unnecessary. File cache pages is still on radix-tree. Don't
* care it.
* __mem_cgroup_commit_charge() check PCG_USED bit of page_cgroup.
* So, double-counting is effectively avoided.
*/
if (!newpage->mapping)
__mem_cgroup_uncharge_common(newpage,
MEM_CGROUP_CHARGE_TYPE_FORCE);
else if (PageAnon(newpage))
mem_cgroup_uncharge_page(newpage);
__mem_cgroup_commit_charge(mem, pc, ctype);
/*
* Both of oldpage and newpage are still under lock_page().
* Then, we don't have to care about race in radix-tree.
* But we have to be careful that this page is unmapped or not.
*
* There is a case for !page_mapped(). At the start of
* migration, oldpage was mapped. But now, it's zapped.
* But we know *target* page is not freed/reused under us.
* mem_cgroup_uncharge_page() does all necessary checks.
*/
if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED)
mem_cgroup_uncharge_page(target);
}
/*