mm: memcontrol: switch to native NR_FILE_PAGES and NR_SHMEM counters

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Link: http://lkml.kernel.org/r/20200508183105.225460-10-hannes@cmpxchg.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 17 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a875a97067a3..ab3497ba0e35 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) *
@@ -3357,7 +3352,7 @@ 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);
@@ -3828,7 +3823,7 @@ 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,
@@ -5461,6 +5456,14 @@ 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);
@@ -6673,10 +6676,8 @@ 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;
 };
 
@@ -6700,9 +6701,7 @@ 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);
@@ -6743,11 +6742,6 @@ 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;