On Thu, May 05, 2011 at 03:47:08PM +0100, David Gilbert wrote: >Hi Kiko, > >On 5 May 2011 15:21, Christian Robottom Reis <k...@linaro.org> wrote: >> Hey there, >> >> I was asked today in the board meeting about the use of NEON >> routines in the kernel; I said we had looked into this but hadn't done >> it because a) it wasn't conclusively better and b) if better, it would >> need to be done conditionally per-platform. But I wanted to double-check >> that's actually true (and I'm copying Vijay to keep me honest). I have >> some references: > >Not quite: > a) Neon memcpy/memset is worse on A9 than non-neon versions (better >on A8 typically)
Yes. Internal hardware differences, apparently. > b) In general I don't believe fpu or Neon code can be used >internally to the kernel. Technically it *can*, but you'll then have to be responsible for dealing with all the extra register save/restores for context switches. Normal wisdom is that it's just not worth that cost unless you're doing an extended amount of such code (e.g. RAID block checksums using Neon). Cheers, -- Steve McIntyre steve.mcint...@linaro.org _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
