Hi Greg, On 29/08/2016 06:28, Gregory Farnum wrote: > On Sun, Aug 28, 2016 at 10:59 AM, Loic Dachary <loic@xxxxxxxxxxx> wrote: >> Hi, >> >> Could we significantly accelerate crush with SIMD instructions ? I don't remember the idea being discussed but maybe I missed it. > > I think it was attempted, but using a lookup table method turned out > to be much faster. Sage did some prototyping and then some folks from > Intel did a lot of heavy optimization; I'd be surprised if anybody > managed to speed up the CRUSH calculations much at this point (at > least, without changing the fundamental math involved). > > Sorry I can't be more detailed; the actual CRUSH implementation is > something I've largely left alone. I imagine the optimization points > become pretty clear running git blame or something though. ;) I was not thinking of accelerating the crush hash function or the straw2 function, but to have them run simultaneously on 4/8/16 items at a time using _mm, _mm256 or _mm512 instructions[1], when possible. I'll put together a proof of concept later today to clarify what I have in mind. Cheers [1] https://software.intel.com/sites/landingpage/IntrinsicsGuide/ -- Loïc Dachary, Artisan Logiciel Libre -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
