We have been relying on the AnonHugePages line of /proc/<pid>/smaps
for informal visibility of huge tmpfs mappings by a process. It's
been good enough, but rather tacky, and best fixed before wider use.
Now reserve AnonHugePages for anonymous THP, and use ShmemHugePages
for huge tmpfs. There is a good argument for calling it ShmemPmdMapped
instead (pte mappings of team pages won't be included in this count),
and I wouldn't mind changing to that; but smaps is all about the mapped,
and I think ShmemHugePages is more what people would expect to see here.
Add a team_page_mapcount() function to help get the PSS accounting right,
now that compound pages are accounting correctly for ptes inside pmds;
but nothing else needs that function, so keep it out of page_mapcount().
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---
Documentation/filesystems/proc.txt | 10 +++++---
Documentation/filesystems/tmpfs.txt | 4 +++
fs/proc/task_mmu.c | 28 ++++++++++++++++--------
include/linux/pageteam.h | 30 ++++++++++++++++++++++++++
4 files changed, 59 insertions(+), 13 deletions(-)
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -435,6 +435,7 @@ Private_Dirty: 0 kB
Referenced: 892 kB
Anonymous: 0 kB
AnonHugePages: 0 kB
+ShmemHugePages: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
@@ -462,10 +463,11 @@ accessed.
"Anonymous" shows the amount of memory that does not belong to any file. Even
a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
and a page is modified, the file page is replaced by a private anonymous copy.
-"AnonHugePages" shows the ammount of memory backed by transparent hugepage.
-"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
-hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
-reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
+"AnonHugePages" shows how much of Anonymous is in Transparent Huge Pages, and
+"ShmemHugePages" shows how much of Rss is from huge tmpfs pages mapped by pmd.
+"Shared_Hugetlb" and "Private_Hugetlb" show the amounts of memory backed by
+hugetlbfs pages: which are not counted in "Rss" or "Pss" fields for historical
+reasons; nor are they included in the {Shared,Private}_{Clean,Dirty} fields.
"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
For shmem mappings, "Swap" includes also the size of the mapped (and not
replaced by copy-on-write) part of the underlying shmem object out on swap.
--- a/Documentation/filesystems/tmpfs.txt
+++ b/Documentation/filesystems/tmpfs.txt
@@ -186,6 +186,10 @@ In addition to 0 and 1, it also accepts
automatically on for all tmpfs mounts (intended for testing), or -1
to force huge off for all (intended for safety if bugs appeared).
+/proc/<pid>/smaps shows:
+
+ShmemHugePages: 10240 kB tmpfs hugepages mapped by pmd into this region
+
/proc/meminfo, /sys/devices/system/node/nodeN/meminfo show:
Shmem: 35016 kB total shmem/tmpfs memory (subset of Cached)
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -14,6 +14,7 @@
#include <linux/swapops.h>
#include <linux/mmu_notifier.h>
#include <linux/page_idle.h>
+#include <linux/pageteam.h>
#include <linux/shmem_fs.h>
#include <asm/elf.h>
@@ -448,6 +449,7 @@ struct mem_size_stats {
unsigned long referenced;
unsigned long anonymous;
unsigned long anonymous_thp;
+ unsigned long shmem_huge;
unsigned long swap;
unsigned long shared_hugetlb;
unsigned long private_hugetlb;
@@ -457,13 +459,19 @@ struct mem_size_stats {
};
static void smaps_account(struct mem_size_stats *mss, struct page *page,
- bool compound, bool young, bool dirty)
+ unsigned long size, bool young, bool dirty)
{
- int i, nr = compound ? 1 << compound_order(page) : 1;
- unsigned long size = nr * PAGE_SIZE;
+ int nr = size / PAGE_SIZE;
+ int i;
- if (PageAnon(page))
+ if (PageAnon(page)) {
mss->anonymous += size;
+ if (size > PAGE_SIZE)
+ mss->anonymous_thp += size;
+ } else {
+ if (size > PAGE_SIZE)
+ mss->shmem_huge += size;
+ }
mss->resident += size;
/* Accumulate the size in pages that have been accessed. */
@@ -473,7 +481,7 @@ static void smaps_account(struct mem_siz
/*
* page_count(page) == 1 guarantees the page is mapped exactly once.
* If any subpage of the compound page mapped with PTE it would elevate
- * page_count().
+ * page_count(). (This condition is never true of mapped pagecache.)
*/
if (page_count(page) == 1) {
if (dirty || PageDirty(page))
@@ -485,7 +493,7 @@ static void smaps_account(struct mem_siz
}
for (i = 0; i < nr; i++, page++) {
- int mapcount = page_mapcount(page);
+ int mapcount = team_page_mapcount(page);
if (mapcount >= 2) {
if (dirty || PageDirty(page))
@@ -561,7 +569,7 @@ static void smaps_pte_entry(pte_t *pte,
if (!page)
return;
- smaps_account(mss, page, false, pte_young(*pte), pte_dirty(*pte));
+ smaps_account(mss, page, PAGE_SIZE, pte_young(*pte), pte_dirty(*pte));
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
@@ -576,8 +584,8 @@ static void smaps_pmd_entry(pmd_t *pmd,
page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
if (IS_ERR_OR_NULL(page))
return;
- mss->anonymous_thp += HPAGE_PMD_SIZE;
- smaps_account(mss, page, true, pmd_young(*pmd), pmd_dirty(*pmd));
+ smaps_account(mss, page, HPAGE_PMD_SIZE,
+ pmd_young(*pmd), pmd_dirty(*pmd));
}
#else
static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
@@ -770,6 +778,7 @@ static int show_smap(struct seq_file *m,
"Referenced: %8lu kB\n"
"Anonymous: %8lu kB\n"
"AnonHugePages: %8lu kB\n"
+ "ShmemHugePages: %8lu kB\n"
"Shared_Hugetlb: %8lu kB\n"
"Private_Hugetlb: %7lu kB\n"
"Swap: %8lu kB\n"
@@ -787,6 +796,7 @@ static int show_smap(struct seq_file *m,
mss.referenced >> 10,
mss.anonymous >> 10,
mss.anonymous_thp >> 10,
+ mss.shmem_huge >> 10,
mss.shared_hugetlb >> 10,
mss.private_hugetlb >> 10,
mss.swap >> 10,
--- a/include/linux/pageteam.h
+++ b/include/linux/pageteam.h
@@ -152,6 +152,36 @@ static inline void count_team_pmd_mapped
}
/*
+ * Slightly misnamed, team_page_mapcount() returns the number of times
+ * any page is mapped into userspace, either by pte or covered by pmd:
+ * it is a generalization of page_mapcount() to include the case of a
+ * team page. We don't complicate page_mapcount() itself in this way,
+ * because almost nothing needs this number: only smaps accounting PSS.
+ * If something else wants it, we might have to worry more about races.
+ */
+static inline int team_page_mapcount(struct page *page)
+{
+ struct page *head;
+ long team_usage;
+ int mapcount;
+
+ mapcount = page_mapcount(page);
+ if (!PageTeam(page))
+ return mapcount;
+ head = team_head(page);
+ /* We always page_add_file_rmap to head when we page_add_team_rmap */
+ if (page == head)
+ return mapcount;
+
+ team_usage = atomic_long_read(&head->team_usage) - TEAM_COMPLETE;
+ /* Beware racing shmem_disband_hugehead() and add_to_swap_cache() */
+ smp_rmb();
+ if (PageTeam(head) && team_usage > 0)
+ mapcount += team_usage / TEAM_MAPPING_COUNTER;
+ return mapcount;
+}
+
+/*
* Returns true if this pte mapping is of a non-team page, or of a team page not
* covered by an existing huge pmd mapping: whereupon stats need to be updated.
* Only called when mapcount goes up from 0 to 1 i.e. _mapcount from -1 to 0.
--
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