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mm: show total hugetlb memory consumption in /proc/meminfo
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Currently we display some hugepage statistics (total, free, etc) in
/proc/meminfo, but only for default hugepage size (e.g.  2Mb).

If hugepages of different sizes are used (like 2Mb and 1Gb on x86-64),
/proc/meminfo output can be confusing, as non-default sized hugepages are
not reflected at all, and there are no signs that they are existing and
consuming system memory.

To solve this problem, let's display the total amount of memory, consumed
by hugetlb pages of all sized (both free and used).  Let's call it
"Hugetlb", and display size in kB to match generic /proc/meminfo style.

For example, (1024 2Mb pages and 2 1Gb pages are pre-allocated):
  $ cat /proc/meminfo
  MemTotal:        8168984 kB
  MemFree:         3789276 kB
  <...>
  CmaFree:               0 kB
  HugePages_Total:    1024
  HugePages_Free:     1024
  HugePages_Rsvd:        0
  HugePages_Surp:        0
  Hugepagesize:       2048 kB
  Hugetlb:         4194304 kB
  DirectMap4k:       32632 kB
  DirectMap2M:     4161536 kB
  DirectMap1G:     6291456 kB

Also, this patch updates corresponding docs to reflect Hugetlb entry
meaning and difference between Hugetlb and HugePages_Total * Hugepagesize.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Roman Gushchin <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: David Rientjes <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: "Aneesh Kumar K.V" <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Dave Hansen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Stephen Rothwell <[email protected]>
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rgushchin authored and sfrothwell committed Nov 30, 2017
1 parent 2e7ea42 commit ec9c6b0
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Showing 2 changed files with 42 additions and 21 deletions.
27 changes: 18 additions & 9 deletions Documentation/vm/hugetlbpage.txt
Original file line number Diff line number Diff line change
Expand Up @@ -20,19 +20,20 @@ options.

The /proc/meminfo file provides information about the total number of
persistent hugetlb pages in the kernel's huge page pool. It also displays
information about the number of free, reserved and surplus huge pages and the
default huge page size. The huge page size is needed for generating the
proper alignment and size of the arguments to system calls that map huge page
regions.
default huge page size and information about the number of free, reserved
and surplus huge pages in the pool of huge pages of default size.
The huge page size is needed for generating the proper alignment and
size of the arguments to system calls that map huge page regions.

The output of "cat /proc/meminfo" will include lines like:

.....
HugePages_Total: vvv
HugePages_Free: www
HugePages_Rsvd: xxx
HugePages_Surp: yyy
Hugepagesize: zzz kB
HugePages_Total: uuu
HugePages_Free: vvv
HugePages_Rsvd: www
HugePages_Surp: xxx
Hugepagesize: yyy kB
Hugetlb: zzz kB

where:
HugePages_Total is the size of the pool of huge pages.
Expand All @@ -47,6 +48,14 @@ HugePages_Surp is short for "surplus," and is the number of huge pages in
the pool above the value in /proc/sys/vm/nr_hugepages. The
maximum number of surplus huge pages is controlled by
/proc/sys/vm/nr_overcommit_hugepages.
Hugepagesize is the default hugepage size (in Kb).
Hugetlb is the total amount of memory (in kB), consumed by huge
pages of all sizes.
If huge pages of different sizes are in use, this number
will exceed HugePages_Total * Hugepagesize. To get more
detailed information, please, refer to
/sys/kernel/mm/hugepages (described below).


/proc/filesystems should also show a filesystem of type "hugetlbfs" configured
in the kernel.
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36 changes: 24 additions & 12 deletions mm/hugetlb.c
Original file line number Diff line number Diff line change
Expand Up @@ -2975,20 +2975,32 @@ int hugetlb_overcommit_handler(struct ctl_table *table, int write,

void hugetlb_report_meminfo(struct seq_file *m)
{
struct hstate *h = &default_hstate;
struct hstate *h;
unsigned long total = 0;

if (!hugepages_supported())
return;
seq_printf(m,
"HugePages_Total: %5lu\n"
"HugePages_Free: %5lu\n"
"HugePages_Rsvd: %5lu\n"
"HugePages_Surp: %5lu\n"
"Hugepagesize: %8lu kB\n",
h->nr_huge_pages,
h->free_huge_pages,
h->resv_huge_pages,
h->surplus_huge_pages,
1UL << (huge_page_order(h) + PAGE_SHIFT - 10));

for_each_hstate(h) {
unsigned long count = h->nr_huge_pages;

total += (PAGE_SIZE << huge_page_order(h)) * count;

if (h == &default_hstate)
seq_printf(m,
"HugePages_Total: %5lu\n"
"HugePages_Free: %5lu\n"
"HugePages_Rsvd: %5lu\n"
"HugePages_Surp: %5lu\n"
"Hugepagesize: %8lu kB\n",
count,
h->free_huge_pages,
h->resv_huge_pages,
h->surplus_huge_pages,
(PAGE_SIZE << huge_page_order(h)) / 1024);
}

seq_printf(m, "Hugetlb: %8lu kB\n", total / 1024);
}

int hugetlb_report_node_meminfo(int nid, char *buf)
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