On Sat, Jun 09, 2007 at 04:23:27PM -0400, Jeff Garzik wrote: > Matt Mackall wrote: > >On Fri, Jun 08, 2007 at 05:42:53PM -0400, Benjamin Gilbert wrote: > >>Add x86-optimized implementation of the SHA-1 hash function, taken from > >>Nettle under the LGPL. This code will be enabled on kernels compiled for > >>486es or better; kernels which support 386es will use the generic > >>implementation (since we need BSWAP). > >> > >>We disable building lib/sha1.o when an optimized implementation is > >>available, as the library link order for x86 (and x86_64) would otherwise > >>ignore the optimized version. The existing optimized implementation for > >>ARM > >>does not do this; the library link order for that architecture appears to > >>favor the arch/arm/ version automatically. I've left this situation alone > >>since I'm not familiar with the ARM code, but a !ARM condition could be > >>added to CONFIG_SHA1_GENERIC if it makes sense. > >> > >>The code has been tested with tcrypt and the NIST test vectors. > > > >Have you benchmarked this against lib/sha1.c? Please post the results. > >Until then, I'm frankly skeptical that your unrolled version is faster > >because when I introduced lib/sha1.c the rolled version therein won by > >a significant margin and had 1/10th the cache footprint. > > Yes. And it also depends on the CPU as well. Testing on a server-class > x86 CPU (often with bigger L2, and perhaps even L1, cache) will produce > different result than from popular but less-capable "value" CPUs. In particular, any optimization made for "486+" CPUs is highly suspect on any machine which runs the core at >1x the memory bus speeds. -- Mathematics is the supreme nostalgia of our time. - To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
