Date: Tue, 9 Mar 2004 17:35:26 +0100
From: Andrea Arcangeli <andrea@suse.de>
To: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@osdl.org>, torvalds@osdl.org,
       linux-kernel@vger.kernel.org
Subject: Re: objrmap-core-1 (rmap removal for file mappings to avoid 4:4 in <=16G machines)
Message-ID: <20040309163526.GL8193@dualathlon.random>
References: <20040308132305.3c35e90a.akpm@osdl.org> <20040308230247.GC12612@dualathlon.random> <20040308152126.54f4f681.akpm@osdl.org> <20040308234014.GG12612@dualathlon.random> <20040309083103.GB8021@elte.hu> <20040309090326.GA10039@elte.hu> <20040309145130.GC8193@dualathlon.random> <20040309150942.GA8224@elte.hu> <20040309152438.GE8193@dualathlon.random> <20040309161051.GA11046@elte.hu>
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On Tue, Mar 09, 2004 at 05:10:51PM +0100, Ingo Molnar wrote:
> 
> * Andrea Arcangeli <andrea@suse.de> wrote:
> 
> > > could you just try test-mmap2.c on such a box, and hit swap?
> 
> > Unless it crashes the machine I don't care, it's totally wrong in my
> > opinion to hurt everything useful to save cpu while running an
> > exploit. there are easier ways to waste cpu (rewrite the exploit with
> > truncate please!!!)
> 
> i'm not sure i follow. "truncate being slow" is not the same order of
> magnitude of a problem as "the VM being incapable of getting work done".

vm has limits, no matter if with rmap or not, if you ask to map 1
million of vmas on a 64bit arch in the same task the rbtree will
slowdown like a crawl too. The vm is a trade-off, we've to optimize for
good apps.
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