[PATCH v6 1/2] mm: hugetlb: proc: add hugetlb-related fields to /proc/PID/smaps

[Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>]

Currently /proc/PID/smaps provides no usage info for vma(VM_HUGETLB), which
is inconvenient when we want to know per-task or per-vma base hugetlb usage.
To solve this, this patch adds new fields for hugetlb usage like below:

  Size:              20480 kB
  Rss:                   0 kB
  Pss:                   0 kB
  Shared_Clean:          0 kB
  Shared_Dirty:          0 kB
  Private_Clean:         0 kB
  Private_Dirty:         0 kB
  Referenced:            0 kB
  Anonymous:             0 kB
  AnonHugePages:         0 kB
  Shared_Hugetlb:    18432 kB
  Private_Hugetlb:     2048 kB
  Swap:                  0 kB
  KernelPageSize:     2048 kB
  MMUPageSize:        2048 kB
  Locked:                0 kB
  VmFlags: rd wr mr mw me de ht

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Joern Engel <joern@logfs.org>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
---
v5 -> v6:
- add comment more to refer to no inclusion in RSS/PSS field
- separate field into {Shared,Private}_Hugetlb (thanks to Pádraig Brady)

v3 -> v4:
- suspend Acked-by tag because v3->v4 change is not trivial
- I stated in previous discussion that HugetlbPages line can contain page
  size info, but that's not necessary because we already have KernelPageSize
  info.
- merged documentation update, where the current documentation doesn't mention
  AnonHugePages, so it's also added.
---
 Documentation/filesystems/proc.txt |  8 ++++++++
 fs/proc/task_mmu.c                 | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git v4.3-rc1/Documentation/filesystems/proc.txt v4.3-rc1_patched/Documentation/filesystems/proc.txt
index d411ca63c8b6..b9467d91052a 100644
--- v4.3-rc1/Documentation/filesystems/proc.txt
+++ v4.3-rc1_patched/Documentation/filesystems/proc.txt
@@ -423,6 +423,9 @@ Private_Clean:         0 kB
 Private_Dirty:         0 kB
 Referenced:          892 kB
 Anonymous:             0 kB
+AnonHugePages:         0 kB
+Shared_Hugetlb:        0 kB
+Private_Hugetlb:        0 kB
 Swap:                  0 kB
 SwapPss:               0 kB
 KernelPageSize:        4 kB
@@ -451,6 +454,11 @@ and a page is modified, the file page is replaced by a private anonymous copy.
 "Swap" shows how much would-be-anonymous memory is also used, but out on
 swap.
 "SwapPss" shows proportional swap share of this mapping.
+"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.
+
 "VmFlags" field deserves a separate description. This member represents the kernel
 flags associated with the particular virtual memory area in two letter encoded
 manner. The codes are the following:
diff --git v4.3-rc1/fs/proc/task_mmu.c v4.3-rc1_patched/fs/proc/task_mmu.c
index e2d46adb54b4..22c02917f265 100644
--- v4.3-rc1/fs/proc/task_mmu.c
+++ v4.3-rc1_patched/fs/proc/task_mmu.c
@@ -446,6 +446,8 @@ struct mem_size_stats {
 	unsigned long anonymous;
 	unsigned long anonymous_thp;
 	unsigned long swap;
+	unsigned long shared_hugetlb;
+	unsigned long private_hugetlb;
 	u64 pss;
 	u64 swap_pss;
 };
@@ -625,12 +627,44 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
 	seq_putc(m, '\n');
 }
 
+#ifdef CONFIG_HUGETLB_PAGE
+static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
+				 unsigned long addr, unsigned long end,
+				 struct mm_walk *walk)
+{
+	struct mem_size_stats *mss = walk->private;
+	struct vm_area_struct *vma = walk->vma;
+	struct page *page = NULL;
+
+	if (pte_present(*pte)) {
+		page = vm_normal_page(vma, addr, *pte);
+	} else if (is_swap_pte(*pte)) {
+		swp_entry_t swpent = pte_to_swp_entry(*pte);
+
+		if (is_migration_entry(swpent))
+			page = migration_entry_to_page(swpent);
+	}
+	if (page) {
+		int mapcount = page_mapcount(page);
+
+		if (mapcount >= 2)
+			mss->shared_hugetlb += huge_page_size(hstate_vma(vma));
+		else
+			mss->private_hugetlb += huge_page_size(hstate_vma(vma));
+	}
+	return 0;
+}
+#endif /* HUGETLB_PAGE */
+
 static int show_smap(struct seq_file *m, void *v, int is_pid)
 {
 	struct vm_area_struct *vma = v;
 	struct mem_size_stats mss;
 	struct mm_walk smaps_walk = {
 		.pmd_entry = smaps_pte_range,
+#ifdef CONFIG_HUGETLB_PAGE
+		.hugetlb_entry = smaps_hugetlb_range,
+#endif
 		.mm = vma->vm_mm,
 		.private = &mss,
 	};
@@ -652,6 +686,8 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
 		   "Referenced:     %8lu kB\n"
 		   "Anonymous:      %8lu kB\n"
 		   "AnonHugePages:  %8lu kB\n"
+		   "Shared_Hugetlb: %8lu kB\n"
+		   "Private_Hugetlb: %8lu kB\n"
 		   "Swap:           %8lu kB\n"
 		   "SwapPss:        %8lu kB\n"
 		   "KernelPageSize: %8lu kB\n"
@@ -667,6 +703,8 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
 		   mss.referenced >> 10,
 		   mss.anonymous >> 10,
 		   mss.anonymous_thp >> 10,
+		   mss.shared_hugetlb >> 10,
+		   mss.private_hugetlb >> 10,
 		   mss.swap >> 10,
 		   (unsigned long)(mss.swap_pss >> (10 + PSS_SHIFT)),
 		   vma_kernel_pagesize(vma) >> 10,
-- 
2.4.3