On Sat, Jun 09, 2007 at 08:33:25PM -0400, Benjamin Gilbert wrote: > Jeff Garzik wrote: > >Matt Mackall wrote: > >>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. > > See the benchmark tables in patch 0 at the head of this thread. > Performance improved by at least 25% in every test, and 40-60% was more > common for the 32-bit version (on a Pentium IV). > > It's not just the loop unrolling; it's the register allocation and > spilling. For comparison, I built SHATransform() from the > drivers/char/random.c in 2.6.11, using gcc 3.3.5 with -O2 and > SHA_CODE_SIZE == 3 (i.e., fully unrolled); I'm guessing this is pretty > close to what you tested back then. The resulting code is 49% MOV > instructions, and 80% of *those* involve memory. gcc4 is somewhat > better, but it still spills a whole lot, both for the 2.6.11 unrolled > code and for the current lib/sha1.c. Wait, your benchmark is comparing against the unrolled code? > In contrast, the assembly implementation in this patch only has to go to > memory for data and workspace (with one small exception in the F3 > rounds), and the workspace has a fifth of the cache footprint of the > default implementation. How big is the -code- footprint? Earlier you wrote: > On the aforementioned Pentium IV, /dev/urandom throughput goes from > 3.7 MB/s to 5.6 MB/s with the patches; on the Core 2, it increases > from 5.5 MB/s to 8.1 MB/s. Whoa. We've regressed something horrible here: http://groups.google.com/group/linux.kernel/msg/fba056363c99d4f9?dmode=source&hl=en In 2003, I was getting 17MB/s out of my Athlon. Now I'm getting 2.7MB/s. Were your tests with or without the latest /dev/urandom fixes? This one in particular: http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.21.y.git;a=commitdiff;h=374f167dfb97c1785515a0c41e32a66b414859a8 -- 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
