mm: memcontrol: convert NR_SHMEM_PMDMAPPED account to pages

Currently we use struct per_cpu_nodestat to cache the vmstat counters,
which leads to inaccurate statistics especially THP vmstat counters.  In
the systems with hundreds of processors it can be GBs of memory.  For
example, for a 96 CPUs system, the threshold is the maximum number of 125.
And the per cpu counters can cache 23.4375 GB in total.

The THP page is already a form of batched addition (it will add 512 worth
of memory in one go) so skipping the batching seems like sensible.
Although every THP stats update overflows the per-cpu counter, resorting
to atomic global updates.  But it can make the statistics more accuracy
for the THP vmstat counters.

So we convert the NR_SHMEM_PMDMAPPED account to pages.  This patch is
consistent with 8f182270dfec ("mm/swap.c: flush lru pvecs on compound page
arrival").  Doing this also can make the unit of vmstat counters more
unified.  Finally, the unit of the vmstat counters are pages, kB and
bytes.  The B/KB suffix can tell us that the unit is bytes or kB.  The
rest which is without suffix are pages.

Link: https://lkml.kernel.org/r/20201228164110.2838-6-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
Cc: Rafael. J. Wysocki <rafael@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 6d5ac6ffb6e1793cdced6cb8d970916c609bfc80..7a66aefe4e46e38ec887c5e22b7cd48008d399a2 100644 (file)
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -463,8 +463,7 @@ static ssize_t node_read_meminfo(struct device *dev,
                             ,
                             nid, K(node_page_state(pgdat, NR_ANON_THPS)),
                             nid, K(node_page_state(pgdat, NR_SHMEM_THPS)),
-                            nid, K(node_page_state(pgdat, NR_SHMEM_PMDMAPPED) *
-                                   HPAGE_PMD_NR),
+                            nid, K(node_page_state(pgdat, NR_SHMEM_PMDMAPPED)),
                             nid, K(node_page_state(pgdat, NR_FILE_THPS)),
                             nid, K(node_page_state(pgdat, NR_FILE_PMDMAPPED) *
                                    HPAGE_PMD_NR)

diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index cfb107eaa3e61c8f614ac4f3160757bc54b4333f..c61f440570f9387e4558d57c0f275b07220de1c5 100644 (file)
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -133,7 +133,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
        show_val_kb(m, "ShmemHugePages: ",
                    global_node_page_state(NR_SHMEM_THPS));
        show_val_kb(m, "ShmemPmdMapped: ",
-                   global_node_page_state(NR_SHMEM_PMDMAPPED) * HPAGE_PMD_NR);
+                   global_node_page_state(NR_SHMEM_PMDMAPPED));
        show_val_kb(m, "FileHugePages:  ",
                    global_node_page_state(NR_FILE_THPS));
        show_val_kb(m, "FilePmdMapped:  ",

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 788837f40b38a080623bc0c24807203e31af1d06..7bdbfeeb5c8c4d688fb2491b8a45eaadecdc0807 100644 (file)
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -221,7 +221,8 @@ static __always_inline bool vmstat_item_print_in_thp(enum node_stat_item item)
 
        return item == NR_ANON_THPS ||
               item == NR_FILE_THPS ||
-              item == NR_SHMEM_THPS;
+              item == NR_SHMEM_THPS ||
+              item == NR_SHMEM_PMDMAPPED;
 }
 
 /*

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index df292d8e659bff6340334d6b7195862a3b136268..069561aadc7be743d6714ac0f7af33c51dbd91dc 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5585,8 +5585,7 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
                        K(node_page_state(pgdat, NR_SHMEM)),
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
                        K(node_page_state(pgdat, NR_SHMEM_THPS)),
-                       K(node_page_state(pgdat, NR_SHMEM_PMDMAPPED)
-                                       * HPAGE_PMD_NR),
+                       K(node_page_state(pgdat, NR_SHMEM_PMDMAPPED)),
                        K(node_page_state(pgdat, NR_ANON_THPS)),
 #endif
                        K(node_page_state(pgdat, NR_WRITEBACK_TEMP)),

diff --git a/mm/rmap.c b/mm/rmap.c
index c4d5c63cfd29dd50ff4335915f75c33830c4707c..1c1b576c06277541ca3e26bcd90bb5729d15574e 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1211,14 +1211,17 @@ void page_add_file_rmap(struct page *page, bool compound)
        VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
        lock_page_memcg(page);
        if (compound && PageTransHuge(page)) {
-               for (i = 0, nr = 0; i < thp_nr_pages(page); i++) {
+               int nr_pages = thp_nr_pages(page);
+
+               for (i = 0, nr = 0; i < nr_pages; i++) {
                        if (atomic_inc_and_test(&page[i]._mapcount))
                                nr++;
                }
                if (!atomic_inc_and_test(compound_mapcount_ptr(page)))
                        goto out;
                if (PageSwapBacked(page))
-                       __inc_node_page_state(page, NR_SHMEM_PMDMAPPED);
+                       __mod_lruvec_page_state(page, NR_SHMEM_PMDMAPPED,
+                                               nr_pages);
                else
                        __inc_node_page_state(page, NR_FILE_PMDMAPPED);
        } else {
@@ -1252,14 +1255,17 @@ static void page_remove_file_rmap(struct page *page, bool compound)
 
        /* page still mapped by someone else? */
        if (compound && PageTransHuge(page)) {
-               for (i = 0, nr = 0; i < thp_nr_pages(page); i++) {
+               int nr_pages = thp_nr_pages(page);
+
+               for (i = 0, nr = 0; i < nr_pages; i++) {
                        if (atomic_add_negative(-1, &page[i]._mapcount))
                                nr++;
                }
                if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
                        return;
                if (PageSwapBacked(page))
-                       __dec_node_page_state(page, NR_SHMEM_PMDMAPPED);
+                       __mod_lruvec_page_state(page, NR_SHMEM_PMDMAPPED,
+                                               -nr_pages);
                else
                        __dec_node_page_state(page, NR_FILE_PMDMAPPED);
        } else {