Re: [PATCH v5 9/9] x86-64: Add CONFIG_UNSAFE_VSYSCALLS tofeature-removal-schedule

From: Ingo Molnar
Date: Mon Jun 06 2011 - 17:54:53 EST

* Andrew Lutomirski <luto@xxxxxxx> 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()?


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