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Date: Mon, 6 Jun 2011 23:54:21 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Andrew Lutomirski <luto@mit.edu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, pageexec@freemail.hu,
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Subject: Re: [PATCH v5 9/9] x86-64: Add CONFIG_UNSAFE_VSYSCALLS to
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* Andrew Lutomirski <luto@mit.edu> wrote:

> > don't even bother making it a config option for now. If we can 
> > replace the vsyscall page with a page fault or int3 or whatever, 
> > and it's only used for the 'time()' system call, just do it.
> 
> Really?
> 
> I won't personally complain about the 200+ ns hit, but I'm sure 
> someone will cc: me on a regression report if there's no option.

Well, for 0.2 usecs to show up one would have to do like a million of 
them per second.

Why an application would want to query the *same value* from the 
kernel a million times per second is beyond me. vgettimeofday()? 
Sure. But vtime()?

Thanks,

	Ingo