linux-kernel - [PATCH v3 3/3] Documentation/filesystems/proc.txt: document hugetlb RSS

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Date:	Mon, 10 Aug 2015 00:47:09 +0000
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Jörn Engel <joern@...estorage.com>
CC:	Mike Kravetz <mike.kravetz@...cle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Naoya Horiguchi <nao.horiguchi@...il.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Subject: [PATCH v3 3/3] Documentation/filesystems/proc.txt: document hugetlb
 RSS

/proc/PID/{status,smaps} is aware of hugetlb RSS now, so let's document it.

Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
---
 Documentation/filesystems/proc.txt | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git v4.2-rc4.orig/Documentation/filesystems/proc.txt v4.2-rc4/Documentation/filesystems/proc.txt
index 6f7fafde0884..cb8565e150ed 100644
--- v4.2-rc4.orig/Documentation/filesystems/proc.txt
+++ v4.2-rc4/Documentation/filesystems/proc.txt
@@ -168,6 +168,7 @@ For example, to get the status information of a process, all you have to do is
   VmLck:         0 kB
   VmHWM:       476 kB
   VmRSS:       476 kB
+  VmHugetlbRSS:  0 kB
   VmData:      156 kB
   VmStk:        88 kB
   VmExe:        68 kB
@@ -230,6 +231,7 @@ Table 1-2: Contents of the status files (as of 4.1)
  VmLck                       locked memory size
  VmHWM                       peak resident set size ("high water mark")
  VmRSS                       size of memory portions
+ VmHugetlbRSS                size of hugetlb memory portions
  VmData                      size of data, stack, and text segments
  VmStk                       size of data, stack, and text segments
  VmExe                       size of text segment
@@ -440,8 +442,12 @@ 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.
+"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
+Since 4.3, "RSS" contains the amount of mappings for hugetlb pages. Although
+RSS of hugetlb mappings is maintained separately from normal mappings
+(displayed in "VmHugetlbRSS" field of /proc/PID/status,) /proc/PID/smaps shows
+both mappings in "RSS" field. Userspace applications clearly distinguish the
+type of mapping with 'ht' flag in "VmFlags" field.
 
 "VmFlags" field deserves a separate description. This member represents the kernel
 flags associated with the particular virtual memory area in two letter encoded
-- 
2.4.3