Commit b2402857 authored by KAMEZAWA Hiroyuki's avatar KAMEZAWA Hiroyuki Committed by Linus Torvalds
Browse files

memcg: remove PCG_CACHE page_cgroup flag 



We record 'the page is cache' with the PCG_CACHE bit in page_cgroup.
Here, "CACHE" means anonymous user pages (and SwapCache).  This doesn't
include shmem.

Considering callers, at charge/uncharge, the caller should know what the
page is and we don't need to record it by using one bit per page.

This patch removes PCG_CACHE bit and make callers of
mem_cgroup_charge_statistics() to specify what the page is.

About page migration: Mapping of the used page is not touched during migra
tion (see page_remove_rmap) so we can rely on it and push the correct
charge type down to __mem_cgroup_uncharge_common from end_migration for
unused page.  The force flag was misleading was abused for skipping the
needless page_mapped() / PageCgroupMigration() check, as we know the
unused page is no longer mapped and cleared the migration flag just a few
lines up.  But doing the checks is no biggie and it's not worth adding
another flag just to skip them.

[akpm@linux-foundation.org: checkpatch fixes]
[hughd@google.com: fix PageAnon uncharging]
Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ying Han <yinghan@google.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ca464d69

include/linux/page_cgroup.h

+1 −7
Original line number Diff line number Diff line
@@ -4,7 +4,6 @@ 
enum {

	/* flags for mem_cgroup */

	PCG_LOCK,  /* Lock for pc->mem_cgroup and following bits. */

	PCG_CACHE, /* charged as cache */

	PCG_USED, /* this object is in use. */

	PCG_MIGRATION, /* under page migration */

	/* flags for mem_cgroup and file and I/O status */
@@ -64,11 +63,6 @@ static inline void ClearPageCgroup##uname(struct page_cgroup *pc) \ 
static inline int TestClearPageCgroup##uname(struct page_cgroup *pc)	\

	{ return test_and_clear_bit(PCG_##lname, &pc->flags);  }



/* Cache flag is set only once (at allocation) */

TESTPCGFLAG(Cache, CACHE)

CLEARPCGFLAG(Cache, CACHE)

SETPCGFLAG(Cache, CACHE)



TESTPCGFLAG(Used, USED)

CLEARPCGFLAG(Used, USED)

SETPCGFLAG(Used, USED)
@@ -85,7 +79,7 @@ static inline void lock_page_cgroup(struct page_cgroup *pc) 
{

	/*

	 * Don't take this lock in IRQ context.

	 * This lock is for pc->mem_cgroup, USED, CACHE, MIGRATION

	 * This lock is for pc->mem_cgroup, USED, MIGRATION

	 */

	bit_spin_lock(PCG_LOCK, &pc->flags);

}

mm/memcontrol.c

+32 −25
Original line number Diff line number Diff line
@@ -690,15 +690,19 @@ static unsigned long mem_cgroup_read_events(struct mem_cgroup *memcg, 
}



static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,

					 bool file, int nr_pages)

					 bool anon, int nr_pages)

{

	preempt_disable();



	if (file)

		__this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],

	/*

	 * Here, RSS means 'mapped anon' and anon's SwapCache. Shmem/tmpfs is

	 * counted as CACHE even if it's on ANON LRU.

	 */

	if (anon)

		__this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],

				nr_pages);

	else

		__this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],

		__this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],

				nr_pages);



	/* pagein of a big page is an event. So, ignore page size */
@@ -2442,6 +2446,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg, 
{

	struct zone *uninitialized_var(zone);

	bool was_on_lru = false;

	bool anon;



	lock_page_cgroup(pc);

	if (unlikely(PageCgroupUsed(pc))) {
@@ -2477,19 +2482,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg, 
	 * See mem_cgroup_add_lru_list(), etc.

 	 */

	smp_wmb();

	switch (ctype) {

	case MEM_CGROUP_CHARGE_TYPE_CACHE:

	case MEM_CGROUP_CHARGE_TYPE_SHMEM:

		SetPageCgroupCache(pc);

		SetPageCgroupUsed(pc);

		break;

	case MEM_CGROUP_CHARGE_TYPE_MAPPED:

		ClearPageCgroupCache(pc);

	SetPageCgroupUsed(pc);

		break;

	default:

		break;

	}



	if (lrucare) {

		if (was_on_lru) {
@@ -2500,7 +2493,12 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg, 
		spin_unlock_irq(&zone->lru_lock);

	}



	mem_cgroup_charge_statistics(memcg, PageCgroupCache(pc), nr_pages);

	if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED)

		anon = true;

	else

		anon = false;



	mem_cgroup_charge_statistics(memcg, anon, nr_pages);

	unlock_page_cgroup(pc);



	/*
@@ -2565,6 +2563,7 @@ static int mem_cgroup_move_account(struct page *page, 
{

	unsigned long flags;

	int ret;

	bool anon = PageAnon(page);



	VM_BUG_ON(from == to);

	VM_BUG_ON(PageLRU(page));
@@ -2593,14 +2592,14 @@ static int mem_cgroup_move_account(struct page *page, 
		__this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);

		preempt_enable();

	}

	mem_cgroup_charge_statistics(from, PageCgroupCache(pc), -nr_pages);

	mem_cgroup_charge_statistics(from, anon, -nr_pages);

	if (uncharge)

		/* This is not "cancel", but cancel_charge does all we need. */

		__mem_cgroup_cancel_charge(from, nr_pages);



	/* caller should have done css_get */

	pc->mem_cgroup = to;

	mem_cgroup_charge_statistics(to, PageCgroupCache(pc), nr_pages);

	mem_cgroup_charge_statistics(to, anon, nr_pages);

	/*

	 * We charges against "to" which may not have any tasks. Then, "to"

	 * can be under rmdir(). But in current implementation, caller of
@@ -2921,6 +2920,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) 
	struct mem_cgroup *memcg = NULL;

	unsigned int nr_pages = 1;

	struct page_cgroup *pc;

	bool anon;



	if (mem_cgroup_disabled())

		return NULL;
@@ -2946,8 +2946,12 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) 
	if (!PageCgroupUsed(pc))

		goto unlock_out;



	anon = PageAnon(page);



	switch (ctype) {

	case MEM_CGROUP_CHARGE_TYPE_MAPPED:

		anon = true;

		/* fallthrough */

	case MEM_CGROUP_CHARGE_TYPE_DROP:

		/* See mem_cgroup_prepare_migration() */

		if (page_mapped(page) || PageCgroupMigration(pc))
@@ -2964,7 +2968,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) 
		break;

	}



	mem_cgroup_charge_statistics(memcg, PageCgroupCache(pc), -nr_pages);

	mem_cgroup_charge_statistics(memcg, anon, -nr_pages);



	ClearPageCgroupUsed(pc);

	/*
@@ -3271,6 +3275,7 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg, 
{

	struct page *used, *unused;

	struct page_cgroup *pc;

	bool anon;



	if (!memcg)

		return;
@@ -3292,8 +3297,10 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg, 
	lock_page_cgroup(pc);

	ClearPageCgroupMigration(pc);

	unlock_page_cgroup(pc);



	__mem_cgroup_uncharge_common(unused, MEM_CGROUP_CHARGE_TYPE_FORCE);

	anon = PageAnon(used);

	__mem_cgroup_uncharge_common(unused,

		anon ? MEM_CGROUP_CHARGE_TYPE_MAPPED

		     : MEM_CGROUP_CHARGE_TYPE_CACHE);



	/*

	 * If a page is a file cache, radix-tree replacement is very atomic
@@ -3303,7 +3310,7 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg, 
	 * and USED bit check in mem_cgroup_uncharge_page() will do enough

	 * check. (see prepare_charge() also)

	 */

	if (PageAnon(used))

	if (anon)

		mem_cgroup_uncharge_page(used);

	/*

	 * At migration, we may charge account against cgroup which has no
@@ -3333,7 +3340,7 @@ void mem_cgroup_replace_page_cache(struct page *oldpage, 
	/* fix accounting on old pages */

	lock_page_cgroup(pc);

	memcg = pc->mem_cgroup;

	mem_cgroup_charge_statistics(memcg, PageCgroupCache(pc), -1);

	mem_cgroup_charge_statistics(memcg, false, -1);

	ClearPageCgroupUsed(pc);

	unlock_page_cgroup(pc);

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