[PATCH v4 1/2] mm: hugetlb: proc: add HugetlbPages field 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 a new line 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
  HugetlbPages:      18432 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>
---
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 |  7 +++++--
 fs/proc/task_mmu.c                 | 29 +++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git v4.2-rc4.orig/Documentation/filesystems/proc.txt v4.2-rc4/Documentation/filesystems/proc.txt
index 6f7fafde0884..22e40211ef64 100644
--- v4.2-rc4.orig/Documentation/filesystems/proc.txt
+++ v4.2-rc4/Documentation/filesystems/proc.txt
@@ -423,6 +423,8 @@ Private_Clean:         0 kB
 Private_Dirty:         0 kB
 Referenced:          892 kB
 Anonymous:             0 kB
+AnonHugePages:         0 kB
+HugetlbPages:          0 kB
 Swap:                  0 kB
 KernelPageSize:        4 kB
 MMUPageSize:           4 kB
@@ -440,8 +442,9 @@ indicates the amount of memory currently marked as referenced or 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.
-"Swap" shows how much would-be-anonymous memory is also used, but out on
-swap.
+"AnonHugePages" shows the ammount of memory backed by transparent hugepage.
+"HugetlbPages" shows the ammount of memory backed by hugetlbfs page.
+"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
 
 "VmFlags" field deserves a separate description. This member represents the kernel
 flags associated with the particular virtual memory area in two letter encoded
diff --git v4.2-rc4.orig/fs/proc/task_mmu.c v4.2-rc4/fs/proc/task_mmu.c
index ca1e091881d4..2c37938b82ee 100644
--- v4.2-rc4.orig/fs/proc/task_mmu.c
+++ v4.2-rc4/fs/proc/task_mmu.c
@@ -445,6 +445,7 @@ struct mem_size_stats {
 	unsigned long anonymous;
 	unsigned long anonymous_thp;
 	unsigned long swap;
+	unsigned long hugetlb;
 	u64 pss;
 };
 
@@ -610,12 +611,38 @@ 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)
+		mss->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,
 	};
@@ -637,6 +664,7 @@ 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"
+		   "HugetlbPages:   %8lu kB\n"
 		   "Swap:           %8lu kB\n"
 		   "KernelPageSize: %8lu kB\n"
 		   "MMUPageSize:    %8lu kB\n"
@@ -651,6 +679,7 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
 		   mss.referenced >> 10,
 		   mss.anonymous >> 10,
 		   mss.anonymous_thp >> 10,
+		   mss.hugetlb >> 10,
 		   mss.swap >> 10,
 		   vma_kernel_pagesize(vma) >> 10,
 		   vma_mmu_pagesize(vma) >> 10,
-- 
2.4.3