Hi, I've started writing ARM/AArch64 NEON optimizations for gf-complete. http://git.jannau.net/gf-complete.git/log/?h=neon has proof of concept AArch64 NEON optimisations for w8. Implemented methods are so far the carry-less/polynomial multiplication and the split table. The polynomial multiplication is reasonable fast for region multiplications (~2000MB/s on an Apple A7 at 1.3GHz) since NEON has a 8-bit to 16-bit SIMD polynomial multiplication. The split table method is still faster though, 5700MB/s on the same CPU. I'm actually surprised by that since it is faster (per cycle) than the Core i7-3770 from gf-complete's manual (page 14). That suggests that SSE3 code might not be optimal. I'm currently working on integrating NEON into the build system and then will extend the existing code to work on ARMv7-a too. Those two are straight forward. There are a couple of other issues I would like to discuss before I start to work on them. The #if/#ifdefs in the source are starting to make the source hard to read then more than one optimization is added. Separating arch specific implementations from each other and from the generic implementation works reasonable well for the multimedia related projects I have experience with (libav/FFmpeg, x264). There would be arch specific init functions which set the appropriate function pointers. The neon optimisations would then live in w8_arm.c which would be only compiled for arm. If someone has another idea how to avoid the #ifdefs I'm open for that too. I'm currently using the SSE/NOSSE region option which is bogus. I'm wondering whether I should just rename that SIMD/NOSIMD (not really true since the carry less operations for w64 and w128 only use the SIMD instruction set but are single data). That would need to have backward compatibility for SSE/NOSSE. The other option would be to add NEON/NONEON flags. I'm sure I find other issues to discuss when I start integrating the NEON optimisations into jerasure and ceph. thanks Janne -- 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
