[PATCH 10/19] mm: memcontrol: switch to native NR_ANON_MAPPED counter

From: Johannes Weiner
Date: Fri May 08 2020 - 14:33:15 EST

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. However, we need to have page->mem_cgroup set
up by the time rmap runs and does the accounting, so switch the commit
and the rmap callbacks around.

v2: fix temporary accounting bug by switching rmap<->commit (Joonsoo)

Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
include/linux/memcontrol.h | 3 +--
kernel/events/uprobes.c | 2 +-
mm/huge_memory.c | 2 +-
mm/khugepaged.c | 2 +-
mm/memcontrol.c | 27 ++++++++--------------
mm/memory.c | 10 ++++----
mm/migrate.c | 2 +-
mm/rmap.c | 47 +++++++++++++++++++++++---------------
mm/swapfile.c | 4 ++--
mm/userfaultfd.c | 2 +-
10 files changed, 51 insertions(+), 50 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index f932e7e9fad8..2df978a3a253 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/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 40e7488ce467..89ef81b65bcb 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -188,8 +188,8 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,

if (new_page) {
get_page(new_page);
- page_add_new_anon_rmap(new_page, vma, addr, false);
mem_cgroup_commit_charge(new_page, memcg, false);
+ page_add_new_anon_rmap(new_page, vma, addr, false);
lru_cache_add_active_or_unevictable(new_page, vma);
} else
/* no new page, just dec_mm_counter for old_page */
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 46c2bc20b7cb..07c012d89570 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -640,8 +640,8 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,

entry = mk_huge_pmd(page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
- page_add_new_anon_rmap(page, vma, haddr, true);
mem_cgroup_commit_charge(page, memcg, false);
+ page_add_new_anon_rmap(page, vma, haddr, true);
lru_cache_add_active_or_unevictable(page, vma);
pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index e2be7f9a92db..be67ebe8a120 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1182,8 +1182,8 @@ static void collapse_huge_page(struct mm_struct *mm,

spin_lock(pmd_ptl);
BUG_ON(!pmd_none(*pmd));
- page_add_new_anon_rmap(new_page, vma, address, true);
mem_cgroup_commit_charge(new_page, memcg, false);
+ page_add_new_anon_rmap(new_page, vma, address, true);
count_memcg_events(memcg, THP_COLLAPSE_ALLOC, 1);
lru_cache_add_active_or_unevictable(new_page, vma);
pgtable_trans_huge_deposit(mm, pmd, pgtable);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c4c060ce1876..fccb396ed7bd 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 {
@@ -3769,7 +3762,7 @@ 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,
@@ -5399,7 +5392,12 @@ 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);

@@ -6530,7 +6528,6 @@ 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())
@@ -6603,8 +6600,6 @@ 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;
@@ -6616,7 +6611,6 @@ 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;
@@ -6641,7 +6635,6 @@ 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);
@@ -6681,8 +6674,6 @@ 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/memory.c b/mm/memory.c
index a08cbaa81607..46c3e5dc918d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2710,8 +2710,8 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
* thread doing COW.
*/
ptep_clear_flush_notify(vma, vmf->address, vmf->pte);
- page_add_new_anon_rmap(new_page, vma, vmf->address, false);
mem_cgroup_commit_charge(new_page, memcg, false);
+ page_add_new_anon_rmap(new_page, vma, vmf->address, false);
lru_cache_add_active_or_unevictable(new_page, vma);
/*
* We call the notify macro here because, when using secondary
@@ -3243,12 +3243,12 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)

/* ksm created a completely new copy */
if (unlikely(page != swapcache && swapcache)) {
- page_add_new_anon_rmap(page, vma, vmf->address, false);
mem_cgroup_commit_charge(page, memcg, false);
+ page_add_new_anon_rmap(page, vma, vmf->address, false);
lru_cache_add_active_or_unevictable(page, vma);
} else {
- do_page_add_anon_rmap(page, vma, vmf->address, exclusive);
mem_cgroup_commit_charge(page, memcg, true);
+ do_page_add_anon_rmap(page, vma, vmf->address, exclusive);
activate_page(page);
}

@@ -3390,8 +3390,8 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
}

inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
- page_add_new_anon_rmap(page, vma, vmf->address, false);
mem_cgroup_commit_charge(page, memcg, false);
+ page_add_new_anon_rmap(page, vma, vmf->address, false);
lru_cache_add_active_or_unevictable(page, vma);
setpte:
set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry);
@@ -3652,8 +3652,8 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
/* copy-on-write page */
if (write && !(vma->vm_flags & VM_SHARED)) {
inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
- page_add_new_anon_rmap(page, vma, vmf->address, false);
mem_cgroup_commit_charge(page, memcg, false);
+ page_add_new_anon_rmap(page, vma, vmf->address, false);
lru_cache_add_active_or_unevictable(page, vma);
} else {
inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page));
diff --git a/mm/migrate.c b/mm/migrate.c
index 3af5447e7aca..e84fb5b87a85 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2838,8 +2838,8 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
goto unlock_abort;

inc_mm_counter(mm, MM_ANONPAGES);
- page_add_new_anon_rmap(page, vma, addr, false);
mem_cgroup_commit_charge(page, memcg, false);
+ page_add_new_anon_rmap(page, vma, addr, false);
if (!is_zone_device_page(page))
lru_cache_add_active_or_unevictable(page, vma);
get_page(page);
diff --git a/mm/rmap.c b/mm/rmap.c
index 2126fd4a254b..e96f1d099c3f 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);
}

/*
diff --git a/mm/swapfile.c b/mm/swapfile.c
index ad42eac1822d..45b937b924f5 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1886,11 +1886,11 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
set_pte_at(vma->vm_mm, addr, pte,
pte_mkold(mk_pte(page, vma->vm_page_prot)));
if (page == swapcache) {
- page_add_anon_rmap(page, vma, addr, false);
mem_cgroup_commit_charge(page, memcg, true);
+ page_add_anon_rmap(page, vma, addr, false);
} else { /* ksm created a completely new copy */
- page_add_new_anon_rmap(page, vma, addr, false);
mem_cgroup_commit_charge(page, memcg, false);
+ page_add_new_anon_rmap(page, vma, addr, false);
lru_cache_add_active_or_unevictable(page, vma);
}
swap_free(entry);
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index bb57d0a3fca7..3dea268d2850 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -123,8 +123,8 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
goto out_release_uncharge_unlock;

inc_mm_counter(dst_mm, MM_ANONPAGES);
- page_add_new_anon_rmap(page, dst_vma, dst_addr, false);
mem_cgroup_commit_charge(page, memcg, false);
+ page_add_new_anon_rmap(page, dst_vma, dst_addr, false);
lru_cache_add_active_or_unevictable(page, dst_vma);

set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
--
2.26.2