Re: [PATCH v5 1/2] mm: hugetlb: proc: add HugetlbPages field to /proc/PID/smaps

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On 08/20/2015 10:26 AM, Naoya Horiguchi wrote:
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@xxxxxxxxxxxxx>
Acked-by: Joern Engel <joern@xxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>

Sorry for coming late to this thread. It's a nice improvement, but I find it somewhat illogical that the per-process stats (status) are more detailed than the per-mapping stats (smaps) with respect to the size breakdown. I would expect it to be the other way around. That would simplify the per-process accounting (I realize this has been a hot topic already), and allow those who really care to look at smaps.

I'm just not sure about the format in that case. In smaps, a line per size would probably make more sense. Even in status, the extra information in parentheses looks somewhat out of place. But of course, adding shared/private breakdown as suggested would lead to an explosion of number of lines in that case...

---
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/Documentation/filesystems/proc.txt v4.2-rc4_patched/Documentation/filesystems/proc.txt
index 6f7fafde0884..22e40211ef64 100644
--- v4.2-rc4/Documentation/filesystems/proc.txt
+++ v4.2-rc4_patched/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/fs/proc/task_mmu.c v4.2-rc4_patched/fs/proc/task_mmu.c
index ca1e091881d4..2c37938b82ee 100644
--- v4.2-rc4/fs/proc/task_mmu.c
+++ v4.2-rc4_patched/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,


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