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Commit 01b1ae63 authored by KAMEZAWA Hiroyuki's avatar KAMEZAWA Hiroyuki Committed by Linus Torvalds
Browse files

memcg: simple migration handling 



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  - if "oldpage" is obsolete, cancel charge of PAGE_SIZE.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: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bced0520

include/linux/memcontrol.h

+7 −12
Original line number Diff line number Diff line
@@ -29,8 +29,6 @@ struct mm_struct; 


extern int mem_cgroup_newpage_charge(struct page *page, struct mm_struct *mm,

				gfp_t gfp_mask);

extern int mem_cgroup_charge_migrate_fixup(struct page *page,

				struct mm_struct *mm, gfp_t gfp_mask);

/* for swap handling */

extern int mem_cgroup_try_charge(struct mm_struct *mm,

		gfp_t gfp_mask, struct mem_cgroup **ptr);
@@ -60,8 +58,9 @@ extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p); 
	((cgroup) == mem_cgroup_from_task((mm)->owner))



extern int

mem_cgroup_prepare_migration(struct page *page, struct page *newpage);

extern void mem_cgroup_end_migration(struct page *page);

mem_cgroup_prepare_migration(struct page *page, struct mem_cgroup **ptr);

extern void mem_cgroup_end_migration(struct mem_cgroup *mem,

	struct page *oldpage, struct page *newpage);



/*

 * For memory reclaim.
@@ -94,12 +93,6 @@ static inline int mem_cgroup_cache_charge(struct page *page, 
	return 0;

}



static inline int mem_cgroup_charge_migrate_fixup(struct page *page,

					struct mm_struct *mm, gfp_t gfp_mask)

{

	return 0;

}



static inline int mem_cgroup_try_charge(struct mm_struct *mm,

				gfp_t gfp_mask, struct mem_cgroup **ptr)

{
@@ -144,12 +137,14 @@ static inline int task_in_mem_cgroup(struct task_struct *task, 
}



static inline int

mem_cgroup_prepare_migration(struct page *page, struct page *newpage)

mem_cgroup_prepare_migration(struct page *page, struct mem_cgroup **ptr)

{

	return 0;

}



static inline void mem_cgroup_end_migration(struct page *page)

static inline void mem_cgroup_end_migration(struct mem_cgroup *mem,

					struct page *oldpage,

					struct page *newpage)

{

}

mm/memcontrol.c

+52 −56
Original line number Diff line number Diff line
@@ -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);

}



/*

mm/migrate.c

+14 −28
Original line number Diff line number Diff line
@@ -121,20 +121,6 @@ static void remove_migration_pte(struct vm_area_struct *vma, 
	if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old)

		goto out;



	/*

	 * Yes, ignore the return value from a GFP_ATOMIC mem_cgroup_charge.

	 * Failure is not an option here: we're now expected to remove every

	 * migration pte, and will cause crashes otherwise.  Normally this

	 * is not an issue: mem_cgroup_prepare_migration bumped up the old

	 * page_cgroup count for safety, that's now attached to the new page,

	 * so this charge should just be another incrementation of the count,

	 * to keep in balance with rmap.c's mem_cgroup_uncharging.  But if

	 * there's been a force_empty, those reference counts may no longer

	 * be reliable, and this charge can actually fail: oh well, we don't

	 * make the situation any worse by proceeding as if it had succeeded.

	 */

	mem_cgroup_charge_migrate_fixup(new, mm, GFP_ATOMIC);



	get_page(new);

	pte = pte_mkold(mk_pte(new, vma->vm_page_prot));

	if (is_write_migration_entry(entry))
@@ -378,9 +364,6 @@ static void migrate_page_copy(struct page *newpage, struct page *page) 
	anon = PageAnon(page);

	page->mapping = NULL;



	if (!anon) /* This page was removed from radix-tree. */

		mem_cgroup_uncharge_cache_page(page);



	/*

	 * If any waiters have accumulated on the new page then

	 * wake them up.
@@ -614,6 +597,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, 
	struct page *newpage = get_new_page(page, private, &result);

	int rcu_locked = 0;

	int charge = 0;

	struct mem_cgroup *mem;



	if (!newpage)

		return -ENOMEM;
@@ -623,24 +607,26 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, 
		goto move_newpage;

	}



	charge = mem_cgroup_prepare_migration(page, newpage);

	if (charge == -ENOMEM) {

		rc = -ENOMEM;

		goto move_newpage;

	}

	/* prepare cgroup just returns 0 or -ENOMEM */

	BUG_ON(charge);



	rc = -EAGAIN;



	if (!trylock_page(page)) {

		if (!force)

			goto move_newpage;

		lock_page(page);

	}



	/* charge against new page */

	charge = mem_cgroup_prepare_migration(page, &mem);

	if (charge == -ENOMEM) {

		rc = -ENOMEM;

		goto unlock;

	}

	BUG_ON(charge);



	if (PageWriteback(page)) {

		if (!force)

			goto unlock;

			goto uncharge;

		wait_on_page_writeback(page);

	}

	/*
@@ -693,7 +679,9 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, 
rcu_unlock:

	if (rcu_locked)

		rcu_read_unlock();



uncharge:

	if (!charge)

		mem_cgroup_end_migration(mem, page, newpage);

unlock:

	unlock_page(page);
@@ -709,8 +697,6 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, 
	}



move_newpage:

	if (!charge)

		mem_cgroup_end_migration(newpage);



	/*

	 * Move the new page to the LRU. If migration was not successful