linux-kernel - Re: [PATCH] Don't mlock guardpage if the stack is growing up

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Date:	Mon, 9 May 2011 16:45:11 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Zdenek Kabelac <zkabelac@...hat.com>
Cc:	Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-parisc@...r.kernel.org,
	Hugh Dickins <hughd@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>, agk@...hat.com
Subject: Re: [PATCH] Don't mlock guardpage if the stack is growing up

On Mon, May 09, 2011 at 01:43:59PM +0200, Zdenek Kabelac wrote:
> > Why it doesn't use mlockall()? Because glibc maps all locales to the 
> > process. Glibc packs all locales to a 100MB file and maps that file to 
> > every process. Even if the process uses just one locale, glibc maps all.
> > 
> > So, when LVM used mlockall, it consumed >100MB memory and it caused 
> > out-of-memory problems in system installers.
> > 
> > So, alternate way of locking was added to LVM --- read all maps and lock 
> > them, except for the glibc locale file.
> > 
> > The real fix would be to fix glibc not to map 100MB to every process.
> 
> I should add here probably few words.
> 
> Glibc knows few more ways around - so it could work only with one locale file
> per language, or even without using mmap and allocating them in memory.
> Depends on the distribution usually - Fedora decided to combine all locales
> into one huge file (>100MB) - Ubuntu/Debian mmaps each locales individually
> (usually ~MB)

Sounds to me like glibc should introduce an mlockmost() call that does all
the work for you ...

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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