[PATCH 10/18] mm: memcontrol: switch to native NR_ANON_MAPPED counter

Johannes Weiner
2020-04-20T22:12:05Z

Memcg maintains a private MEMCG_RSS counter. This divergence from the
generic VM accounting means unnecessary code overhead, and creates a
dependency for memcg that page->mapping is set up at the time of
charging, so that page types can be told apart.

Convert the generic accounting sites to mod_lruvec_page_state and
friends to maintain the per-cgroup vmstat counter of
NR_ANON_MAPPED. We use lock_page_memcg() to stabilize page->mem_cgroup
during rmap changes, the same way we do for NR_FILE_MAPPED.

With the previous patch removing MEMCG_CACHE and the private NR_SHMEM
counter, this patch finally eliminates the need to have page->mapping
set up at charge time.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
include/linux/memcontrol.h | 3 +--
mm/memcontrol.c | 27 ++++++++--------------
mm/rmap.c | 47 +++++++++++++++++++++++---------------
3 files changed, 39 insertions(+), 38 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index c44aa1ccf553..bfb1d961e346 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -29,8 +29,7 @@ struct kmem_cache;

/* Cgroup-specific page state, on top of universal node page state */
enum memcg_stat_item {
- MEMCG_RSS = NR_VM_NODE_STAT_ITEMS,
- MEMCG_RSS_HUGE,
+ MEMCG_RSS_HUGE = NR_VM_NODE_STAT_ITEMS,
MEMCG_SWAP,
MEMCG_SOCK,
/* XXX: why are these zone and not node counters? */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7e77166cf10b..c87178d6219f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -836,13 +836,6 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
struct page *page,
int nr_pages)
{
- /*
- * Here, RSS means 'mapped anon' and anon's SwapCache. Shmem/tmpfs is
- * counted as CACHE even if it's on ANON LRU.
- */
- if (PageAnon(page))
- __mod_memcg_state(memcg, MEMCG_RSS, nr_pages);
-
if (abs(nr_pages) > 1) {
VM_BUG_ON_PAGE(!PageTransHuge(page), page);
__mod_memcg_state(memcg, MEMCG_RSS_HUGE, nr_pages);
@@ -1384,7 +1377,7 @@ static char *memory_stat_format(struct mem_cgroup *memcg)
*/

seq_buf_printf(&s, "anon %llu\n",
- (u64)memcg_page_state(memcg, MEMCG_RSS) *
+ (u64)memcg_page_state(memcg, NR_ANON_MAPPED) *
PAGE_SIZE);
seq_buf_printf(&s, "file %llu\n",
(u64)memcg_page_state(memcg, NR_FILE_PAGES) *
@@ -3298,7 +3291,7 @@ static unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)

if (mem_cgroup_is_root(memcg)) {
val = memcg_page_state(memcg, NR_FILE_PAGES) +
- memcg_page_state(memcg, MEMCG_RSS);
+ memcg_page_state(memcg, NR_ANON_MAPPED);
if (swap)
val += memcg_page_state(memcg, MEMCG_SWAP);
} else {
@@ -3768,7 +3761,7 @@ static int memcg_numa_stat_show(struct seq_file *m, void *v)

static const unsigned int memcg1_stats[] = {
NR_FILE_PAGES,
- MEMCG_RSS,
+ NR_ANON_MAPPED,
MEMCG_RSS_HUGE,
NR_SHMEM,
NR_FILE_MAPPED,
@@ -5395,7 +5388,12 @@ static int mem_cgroup_move_account(struct page *page,

lock_page_memcg(page);

- if (!PageAnon(page)) {
+ if (PageAnon(page)) {
+ if (page_mapped(page)) {
+ __mod_lruvec_state(from_vec, NR_ANON_MAPPED, -nr_pages);
+ __mod_lruvec_state(to_vec, NR_ANON_MAPPED, nr_pages);
+ }
+ } else {
__mod_lruvec_state(from_vec, NR_FILE_PAGES, -nr_pages);
__mod_lruvec_state(to_vec, NR_FILE_PAGES, nr_pages);

@@ -6529,7 +6527,6 @@ void mem_cgroup_commit_charge(struct page *page, struct mem_cgroup *memcg,
{
unsigned int nr_pages = hpage_nr_pages(page);

- VM_BUG_ON_PAGE(!page->mapping, page);
VM_BUG_ON_PAGE(PageLRU(page) && !lrucare, page);

if (mem_cgroup_disabled())
@@ -6602,8 +6599,6 @@ int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask,
struct mem_cgroup *memcg;
int ret;

- VM_BUG_ON_PAGE(!page->mapping, page);
-
ret = mem_cgroup_try_charge(page, mm, gfp_mask, &memcg);
if (ret)
return ret;
@@ -6615,7 +6610,6 @@ struct uncharge_gather {
struct mem_cgroup *memcg;
unsigned long nr_pages;
unsigned long pgpgout;
- unsigned long nr_anon;
unsigned long nr_kmem;
unsigned long nr_huge;
struct page *dummy_page;
@@ -6640,7 +6634,6 @@ static void uncharge_batch(const struct uncharge_gather *ug)
}

local_irq_save(flags);
- __mod_memcg_state(ug->memcg, MEMCG_RSS, -ug->nr_anon);
__mod_memcg_state(ug->memcg, MEMCG_RSS_HUGE, -ug->nr_huge);
__count_memcg_events(ug->memcg, PGPGOUT, ug->pgpgout);
__this_cpu_add(ug->memcg->vmstats_percpu->nr_page_events, ug->nr_pages);
@@ -6682,8 +6675,6 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
if (!PageKmemcg(page)) {
if (PageTransHuge(page))
ug->nr_huge += nr_pages;
- if (PageAnon(page))
- ug->nr_anon += nr_pages;
ug->pgpgout++;
} else {
ug->nr_kmem += nr_pages;
diff --git a/mm/rmap.c b/mm/rmap.c
index f79a206b271a..150513d31efa 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1114,6 +1114,11 @@ void do_page_add_anon_rmap(struct page *page,
bool compound = flags & RMAP_COMPOUND;
bool first;

+ if (unlikely(PageKsm(page)))
+ lock_page_memcg(page);
+ else
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+
if (compound) {
atomic_t *mapcount;
VM_BUG_ON_PAGE(!PageLocked(page), page);
@@ -1134,12 +1139,13 @@ void do_page_add_anon_rmap(struct page *page,
*/
if (compound)
__inc_node_page_state(page, NR_ANON_THPS);
- __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr);
+ __mod_lruvec_page_state(page, NR_ANON_MAPPED, nr);
}
- if (unlikely(PageKsm(page)))
- return;

- VM_BUG_ON_PAGE(!PageLocked(page), page);
+ if (unlikely(PageKsm(page))) {
+ unlock_page_memcg(page);
+ return;
+ }

/* address might be in next vma when migration races vma_adjust */
if (first)
@@ -1181,7 +1187,7 @@ void page_add_new_anon_rmap(struct page *page,
/* increment count (starts at -1) */
atomic_set(&page->_mapcount, 0);
}
- __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr);
+ __mod_lruvec_page_state(page, NR_ANON_MAPPED, nr);
__page_set_anon_rmap(page, vma, address, 1);
}

@@ -1230,13 +1236,12 @@ static void page_remove_file_rmap(struct page *page, bool compound)
int i, nr = 1;

VM_BUG_ON_PAGE(compound && !PageHead(page), page);
- lock_page_memcg(page);

/* Hugepages are not counted in NR_FILE_MAPPED for now. */
if (unlikely(PageHuge(page))) {
/* hugetlb pages are always mapped with pmds */
atomic_dec(compound_mapcount_ptr(page));
- goto out;
+ return;
}

/* page still mapped by someone else? */
@@ -1246,14 +1251,14 @@ static void page_remove_file_rmap(struct page *page, bool compound)
nr++;
}
if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
- goto out;
+ return;
if (PageSwapBacked(page))
__dec_node_page_state(page, NR_SHMEM_PMDMAPPED);
else
__dec_node_page_state(page, NR_FILE_PMDMAPPED);
} else {
if (!atomic_add_negative(-1, &page->_mapcount))
- goto out;
+ return;
}

/*
@@ -1265,8 +1270,6 @@ static void page_remove_file_rmap(struct page *page, bool compound)

if (unlikely(PageMlocked(page)))
clear_page_mlock(page);
-out:
- unlock_page_memcg(page);
}

static void page_remove_anon_compound_rmap(struct page *page)
@@ -1310,7 +1313,7 @@ static void page_remove_anon_compound_rmap(struct page *page)
clear_page_mlock(page);

if (nr)
- __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, -nr);
+ __mod_lruvec_page_state(page, NR_ANON_MAPPED, -nr);
}

/**
@@ -1322,22 +1325,28 @@ static void page_remove_anon_compound_rmap(struct page *page)
*/
void page_remove_rmap(struct page *page, bool compound)
{
- if (!PageAnon(page))
- return page_remove_file_rmap(page, compound);
+ lock_page_memcg(page);

- if (compound)
- return page_remove_anon_compound_rmap(page);
+ if (!PageAnon(page)) {
+ page_remove_file_rmap(page, compound);
+ goto out;
+ }
+
+ if (compound) {
+ page_remove_anon_compound_rmap(page);
+ goto out;
+ }

/* page still mapped by someone else? */
if (!atomic_add_negative(-1, &page->_mapcount))
- return;
+ goto out;

/*
* We use the irq-unsafe __{inc|mod}_zone_page_stat because
* these counters are not modified in interrupt context, and
* pte lock(a spinlock) is held, which implies preemption disabled.
*/
- __dec_node_page_state(page, NR_ANON_MAPPED);
+ __dec_lruvec_page_state(page, NR_ANON_MAPPED);

if (unlikely(PageMlocked(page)))
clear_page_mlock(page);
@@ -1354,6 +1363,8 @@ void page_remove_rmap(struct page *page, bool compound)
* Leaving it set also helps swapoff to reinstate ptes
* faster for those pages still in swapcache.
*/
+out:
+ unlock_page_memcg(page);
}

/*
--
2.26.0