linux-kernel - Re: [PATCH] Hugepages should be accounted as unevictable pages.

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Message-Id: <20090623150630.31c0dff5.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 23 Jun 2009 15:06:30 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	akataria@...are.com
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Mel Gorman <mel@....ul.ie>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH] Hugepages should be accounted as unevictable pages.

On Mon, 22 Jun 2009 22:54:01 -0700
Alok Kataria <akataria@...are.com> wrote:

> > > 
> > > I don't have any strong oppose reason, but I also don't have any strong
> > > agree reason.
> > > 
> > I think "don't include Hugepage" is sane. Hugepage is something _special_, now.
> > 
> Kamezawa-san, 
> 
> I agree that hugepages are special in the sense that they are
> implemented specially and don't actually reside on the LRU like any
> other locked memory. But, both of these memory types (mlocked and
> hugepages) are actually unevictable and can't be reclaimed back, so i
> don't see a reason why should accounting not reflect that.
> 

I bet we should rename "Unevictable" to "Mlocked" or "Pinned" rather than
take nr_hugepages into account. I think this "Unevictable" in meminfo means
- pages which are evictable in their nature (because in LRU) but a user pinned it -

How about rename "Unevictable" to "Pinned" or "Locked" ?
(Mlocked + locked shmem's + ramfs?)

We have other "unevictable" pages other than Hugepage anyway.
 - page table
 - some slab
 - kernel's page
 - anon pages in swapless system
 etc...

BTW, I use following calculation for quick check if I want all "Unevicatable" pages.

Unevictable = Total - (Active+Inactive) + (50-70%? of slab)

This # of is not-reclaimable memory.

Thanks,
-Kame


> Thanks,
> Alok
> 
> > Thanks,
> > -Kame
> > 
> 
> 

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