Messages in this thread | | | Date | Thu, 21 Nov 2002 18:18:18 +0000 | From | Dave Jones <> | Subject | Re: [BENCHMARK] 2.5.47{-mm1} with contest |
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On Thu, Nov 21, 2002 at 09:21:47AM -0800, Andrew Morton wrote:
> > Good eyes. But.. this also applies to 2.4 (which should also then > > get faster). So the gap between 2.4 & 2.5 must be somewhere else ? > > But 2.4 already inlines the usercopy functions. With this benchmark, > the cost of the function call is visible. Same with the dir_rtn_1 > test - it is performing zillions of 3, 7, 10-byte copies into userspace.
But the reduction of number of copy_*_user's applies to 2.4 too right ?
> We'd buy a bit by arranging for the in-kernel copy of the fp state > to have the same layout as the hardware. That way it can be done in > a single big, fast, well-aligned slurp. But for some reason that code has > to convert into and out of a different representation.
Possibly hardware restrictions, I'm unfamiliar with how this voodoo works.
> But the real low-hanging fruit here is the observation that the > test application doesn't use floating point!!!
Interesting point. What was the test app ? contest ? (I missed the beginning of this thread).
> Maybe we need to take an fp trap now and then to "poll" the application > to see if it is still using float.
Neat idea. Bonus points for making it work 8-)
Dave
-- | Dave Jones. http://www.codemonkey.org.uk | SuSE Labs - 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/
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