lkml.org 
[lkml]   [2005]   [Jul]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [patch 2.6.13-rc3a] i386: inline restore_fpu
From
Date
Andrew Morton <akpm@osdl.org> writes:
>
> We do have the `used_math' optimisation in there which attempts to avoid
> doing the FP save/restore if the app isn't actually using math. But
> <ancient recollections> there's code in glibc startup which always does a
> bit of float, so that optimisation is always defeated. There was some
> discussion about periodically setting tasks back into !used_math state to
> try to restore the optimisation for tasks which only do a little bit of FP,
> but nothing actually got done.

Actually we reset the flag on every context switch, so that works just fine.

But I was considering to do it less often so that we switch the FP
state non lazily for FP intensive processes and avoid the overhead
of all these exceptions.

-Andi

P.S.: Original profile data looks a bit fishy. Normally avoiding a single
function call should not make tht much difference unless you call
it in a inner loop, but that is not the case here.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-07-23 17:40    [W:0.041 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site