[PATCH 09/18] mm: memcontrol: switch to native NR_FILE_PAGES and NR_SHMEM counters

Johannes Weiner
2020-04-20T22:12:01Z

Memcg maintains private MEMCG_CACHE and NR_SHMEM counters. 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 counters of NR_FILE_PAGES
and NR_SHMEM. The page is already locked in these places, so
page->mem_cgroup is stable; we only need minimal tweaks of two
mem_cgroup_migrate() calls to ensure it's set up in time.

Then replace MEMCG_CACHE with NR_FILE_PAGES and delete the private
NR_SHMEM accounting sites.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
include/linux/memcontrol.h | 3 +--
mm/filemap.c | 17 +++++++++--------
mm/khugepaged.c | 16 +++++++++++-----
mm/memcontrol.c | 28 +++++++++++-----------------
mm/migrate.c | 15 +++++++++++----
mm/shmem.c | 14 +++++++-------
6 files changed, 50 insertions(+), 43 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 5a1b5a7b7728..c44aa1ccf553 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_CACHE = NR_VM_NODE_STAT_ITEMS,
- MEMCG_RSS,
+ MEMCG_RSS = NR_VM_NODE_STAT_ITEMS,
MEMCG_RSS_HUGE,
MEMCG_SWAP,
MEMCG_SOCK,
diff --git a/mm/filemap.c b/mm/filemap.c
index 5bdbda965177..f4592ff3ca8b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -199,9 +199,9 @@ static void unaccount_page_cache_page(struct address_space *mapping,

nr = hpage_nr_pages(page);

- __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
+ __mod_lruvec_page_state(page, NR_FILE_PAGES, -nr);
if (PageSwapBacked(page)) {
- __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
+ __mod_lruvec_page_state(page, NR_SHMEM, -nr);
if (PageTransHuge(page))
__dec_node_page_state(page, NR_SHMEM_THPS);
} else if (PageTransHuge(page)) {
@@ -802,21 +802,22 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
new->mapping = mapping;
new->index = offset;

+ mem_cgroup_migrate(old, new);
+
xas_lock_irqsave(&xas, flags);
xas_store(&xas, new);

old->mapping = NULL;
/* hugetlb pages do not participate in page cache accounting. */
if (!PageHuge(old))
- __dec_node_page_state(old, NR_FILE_PAGES);
+ __dec_lruvec_page_state(old, NR_FILE_PAGES);
if (!PageHuge(new))
- __inc_node_page_state(new, NR_FILE_PAGES);
+ __inc_lruvec_page_state(new, NR_FILE_PAGES);
if (PageSwapBacked(old))
- __dec_node_page_state(old, NR_SHMEM);
+ __dec_lruvec_page_state(old, NR_SHMEM);
if (PageSwapBacked(new))
- __inc_node_page_state(new, NR_SHMEM);
+ __inc_lruvec_page_state(new, NR_SHMEM);
xas_unlock_irqrestore(&xas, flags);
- mem_cgroup_migrate(old, new);
if (freepage)
freepage(old);
put_page(old);
@@ -867,7 +868,7 @@ static int __add_to_page_cache_locked(struct page *page,

/* hugetlb pages do not participate in page cache accounting */
if (!huge)
- __inc_node_page_state(page, NR_FILE_PAGES);
+ __inc_lruvec_page_state(page, NR_FILE_PAGES);
unlock:
xas_unlock_irq(&xas);
} while (xas_nomem(&xas, gfp_mask & GFP_RECLAIM_MASK));
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 46f9b565e8d5..ee2ef4b8e828 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1740,12 +1740,18 @@ static void collapse_file(struct mm_struct *mm,
}

if (nr_none) {
- struct zone *zone = page_zone(new_page);
-
- __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
+ struct lruvec *lruvec;
+ /*
+ * XXX: We have started try_charge and pinned the
+ * memcg, but the page isn't committed yet so we
+ * cannot use mod_lruvec_page_state(). This hackery
+ * will be cleaned up when remove the page->mapping
+ * dependency from memcg and fully charge above.
+ */
+ lruvec = mem_cgroup_lruvec(memcg, page_pgdat(new_page));
+ __mod_lruvec_state(lruvec, NR_FILE_PAGES, nr_none);
if (is_shmem)
- __mod_node_page_state(zone->zone_pgdat,
- NR_SHMEM, nr_none);
+ __mod_lruvec_state(lruvec, NR_SHMEM, nr_none);
}

xa_locked:
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e9e22c86a118..7e77166cf10b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -842,11 +842,6 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
*/
if (PageAnon(page))
__mod_memcg_state(memcg, MEMCG_RSS, nr_pages);
- else {
- __mod_memcg_state(memcg, MEMCG_CACHE, nr_pages);
- if (PageSwapBacked(page))
- __mod_memcg_state(memcg, NR_SHMEM, nr_pages);
- }

if (abs(nr_pages) > 1) {
VM_BUG_ON_PAGE(!PageTransHuge(page), page);
@@ -1392,7 +1387,7 @@ static char *memory_stat_format(struct mem_cgroup *memcg)
(u64)memcg_page_state(memcg, MEMCG_RSS) *
PAGE_SIZE);
seq_buf_printf(&s, "file %llu\n",
- (u64)memcg_page_state(memcg, MEMCG_CACHE) *
+ (u64)memcg_page_state(memcg, NR_FILE_PAGES) *
PAGE_SIZE);
seq_buf_printf(&s, "kernel_stack %llu\n",
(u64)memcg_page_state(memcg, MEMCG_KERNEL_STACK_KB) *
@@ -3302,7 +3297,7 @@ static unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
unsigned long val;

if (mem_cgroup_is_root(memcg)) {
- val = memcg_page_state(memcg, MEMCG_CACHE) +
+ val = memcg_page_state(memcg, NR_FILE_PAGES) +
memcg_page_state(memcg, MEMCG_RSS);
if (swap)
val += memcg_page_state(memcg, MEMCG_SWAP);
@@ -3772,7 +3767,7 @@ static int memcg_numa_stat_show(struct seq_file *m, void *v)
#endif /* CONFIG_NUMA */

static const unsigned int memcg1_stats[] = {
- MEMCG_CACHE,
+ NR_FILE_PAGES,
MEMCG_RSS,
MEMCG_RSS_HUGE,
NR_SHMEM,
@@ -5401,6 +5396,14 @@ static int mem_cgroup_move_account(struct page *page,
lock_page_memcg(page);

if (!PageAnon(page)) {
+ __mod_lruvec_state(from_vec, NR_FILE_PAGES, -nr_pages);
+ __mod_lruvec_state(to_vec, NR_FILE_PAGES, nr_pages);
+
+ if (PageSwapBacked(page)) {
+ __mod_lruvec_state(from_vec, NR_SHMEM, -nr_pages);
+ __mod_lruvec_state(to_vec, NR_SHMEM, nr_pages);
+ }
+
if (page_mapped(page)) {
__mod_lruvec_state(from_vec, NR_FILE_MAPPED, -nr_pages);
__mod_lruvec_state(to_vec, NR_FILE_MAPPED, nr_pages);
@@ -6613,10 +6616,8 @@ struct uncharge_gather {
unsigned long nr_pages;
unsigned long pgpgout;
unsigned long nr_anon;
- unsigned long nr_file;
unsigned long nr_kmem;
unsigned long nr_huge;
- unsigned long nr_shmem;
struct page *dummy_page;
};

@@ -6640,9 +6641,7 @@ 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_CACHE, -ug->nr_file);
__mod_memcg_state(ug->memcg, MEMCG_RSS_HUGE, -ug->nr_huge);
- __mod_memcg_state(ug->memcg, NR_SHMEM, -ug->nr_shmem);
__count_memcg_events(ug->memcg, PGPGOUT, ug->pgpgout);
__this_cpu_add(ug->memcg->vmstats_percpu->nr_page_events, ug->nr_pages);
memcg_check_events(ug->memcg, ug->dummy_page);
@@ -6685,11 +6684,6 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
ug->nr_huge += nr_pages;
if (PageAnon(page))
ug->nr_anon += nr_pages;
- else {
- ug->nr_file += nr_pages;
- if (PageSwapBacked(page))
- ug->nr_shmem += nr_pages;
- }
ug->pgpgout++;
} else {
ug->nr_kmem += nr_pages;
diff --git a/mm/migrate.c b/mm/migrate.c
index 5dd50128568c..14a584c52782 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -490,11 +490,18 @@ int migrate_page_move_mapping(struct address_space *mapping,
* are mapped to swap space.
*/
if (newzone != oldzone) {
- __dec_node_state(oldzone->zone_pgdat, NR_FILE_PAGES);
- __inc_node_state(newzone->zone_pgdat, NR_FILE_PAGES);
+ struct lruvec *old_lruvec, *new_lruvec;
+ struct mem_cgroup *memcg;
+
+ memcg = page_memcg(page);
+ old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat);
+ new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat);
+
+ __dec_lruvec_state(old_lruvec, NR_FILE_PAGES);
+ __inc_lruvec_state(new_lruvec, NR_FILE_PAGES);
if (PageSwapBacked(page) && !PageSwapCache(page)) {
- __dec_node_state(oldzone->zone_pgdat, NR_SHMEM);
- __inc_node_state(newzone->zone_pgdat, NR_SHMEM);
+ __dec_lruvec_state(old_lruvec, NR_SHMEM);
+ __inc_lruvec_state(new_lruvec, NR_SHMEM);
}
if (dirty && mapping_cap_account_dirty(mapping)) {
__dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
diff --git a/mm/shmem.c b/mm/shmem.c
index 2384f6c7ef71..363bd11eba85 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -653,8 +653,8 @@ static int shmem_add_to_page_cache(struct page *page,
__inc_node_page_state(page, NR_SHMEM_THPS);
}
mapping->nrpages += nr;
- __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
- __mod_node_page_state(page_pgdat(page), NR_SHMEM, nr);
+ __mod_lruvec_page_state(page, NR_FILE_PAGES, nr);
+ __mod_lruvec_page_state(page, NR_SHMEM, nr);
unlock:
xas_unlock_irq(&xas);
} while (xas_nomem(&xas, gfp));
@@ -685,8 +685,8 @@ static void shmem_delete_from_page_cache(struct page *page, void *radswap)
error = shmem_replace_entry(mapping, page->index, page, radswap);
page->mapping = NULL;
mapping->nrpages--;
- __dec_node_page_state(page, NR_FILE_PAGES);
- __dec_node_page_state(page, NR_SHMEM);
+ __dec_lruvec_page_state(page, NR_FILE_PAGES);
+ __dec_lruvec_page_state(page, NR_SHMEM);
xa_unlock_irq(&mapping->i_pages);
put_page(page);
BUG_ON(error);
@@ -1593,8 +1593,9 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
xa_lock_irq(&swap_mapping->i_pages);
error = shmem_replace_entry(swap_mapping, swap_index, oldpage, newpage);
if (!error) {
- __inc_node_page_state(newpage, NR_FILE_PAGES);
- __dec_node_page_state(oldpage, NR_FILE_PAGES);
+ mem_cgroup_migrate(oldpage, newpage);
+ __inc_lruvec_page_state(newpage, NR_FILE_PAGES);
+ __dec_lruvec_page_state(oldpage, NR_FILE_PAGES);
}
xa_unlock_irq(&swap_mapping->i_pages);

@@ -1606,7 +1607,6 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
*/
oldpage = newpage;
} else {
- mem_cgroup_migrate(oldpage, newpage);
lru_cache_add_anon(newpage);
*pagep = newpage;
}
--
2.26.0