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

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Message-ID: <20150820232011.GA10807@hori1.linux.bs1.fc.nec.co.jp>
Date:	Thu, 20 Aug 2015 23:20:12 +0000
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Michal Hocko <mhocko@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Jörn Engel <joern@...estorage.com>,
	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>
Subject: Re: [PATCH v5 1/2] mm: hugetlb: proc: add HugetlbPages field to
 /proc/PID/smaps

On Thu, Aug 20, 2015 at 12:49:29PM +0200, Michal Hocko wrote:
> On Thu 20-08-15 08:26:26, 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
> 
> I have only now got to this thread. This is indeed very helpful. I would
> just suggest to update Documentation/filesystems/proc.txt to be explicit
> that Rss: doesn't count hugetlb pages for historical reasons.

I agree, I want the following diff to be folded to this patch.

>  
> > Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> > Acked-by: Joern Engel <joern@...fs.org>
> > Acked-by: David Rientjes <rientjes@...gle.com>
> 
> Acked-by: Michal Hocko <mhocko@...e.cz>

Thank you.
Naoya Horiguchi
---
From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Date: Fri, 21 Aug 2015 08:13:31 +0900
Subject: [PATCH] Documentation/filesystems/proc.txt: give additional comment
 about hugetlb usage

---
 Documentation/filesystems/proc.txt | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index f561fc46e41b..b775b6faaeda 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -446,7 +446,8 @@ indicates the amount of memory currently marked as referenced or accessed.
 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.
 "AnonHugePages" shows the ammount of memory backed by transparent hugepage.
-"HugetlbPages" shows the ammount of memory backed by hugetlbfs page.
+"HugetlbPages" shows the ammount of memory backed by hugetlbfs page (which is
+not counted in "Rss" or "Pss" field for historical reasons.)
 "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
-- 
2.4.3