Re: [PATCH] [LSM] Rework LSM hooks

[Chris Wright <chrisw@osdl.org>]

* David Mosberger (davidm@napali.hpl.hp.com) wrote:
> >>>>> On Tue, 10 Aug 2004 16:31:12 -0400 (EDT), James Morris <jmorris@redhat.com> said:
> 
>   James> On Tue, 10 Aug 2004, Chris Wright wrote:
>   >> Thanks, James.  Since these are the only concrete numbers and
>   >> they are in the noise, I see no compelling reason to change to
>   >> unlikely().
> 
>   James> There may be some way to make it ia64 specific.  Is it a cpu
>   James> issue, or compiler?
> 
> I'm pretty sure the "unlikely()" part could be dropped with little/no
> downside.  The part that's relatively expensive (10 cycles when
> mispredicted) is the indirect call.  GCC doesn't handle this well on
> ia64 and as a result, most indirect calls are mispredicted.
> 
> An alternative solution might be to have a call_likely() macro, where
> you could predict the most likely target of an indirect call.  Perhaps
> that could help other platforms as well.

Hmm, the pointers are generally quite static, set once near boot time
typically, and that's it.  Seems like a plausible win.  Do you have an
example of what call_likely() would look like?

thanks,
-chris
-- 
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