On Thu, 6 Aug 2009, Linus Torvalds wrote: > > Hmm. Ok, I just tested with your harness, and I get > > # TIME[s] SPEED[MB/s] > rfc3174 5.1 119.7 > rfc3174 5.097 119.7 > linus 1.836 332.5 > linusas 2.006 304.3 > linusas2 1.879 324.9 > mozilla 5.562 109.7 > mozillaas 5.913 103.2 > openssl 1.613 378.5 > spelvin 1.698 359.5 > spelvina 1.602 381 > nettle 1.594 382.9 On atom, I get things like: # TIME[s] SPEED[MB/s] rfc3174 2.186 27.92 rfc3174 2.186 27.92 linus 0.9492 64.3 linusas 0.9656 63.21 linusas2 1.012 60.29 mozilla 2.492 24.49 mozillaas 2.5 24.41 openssl 0.6411 95.2 spelvin 0.6052 100.8 spelvina 0.6655 91.71 nettle 0.7149 85.37 but quite frankly, those timings aren't stable enough to say anything. Another few runs got me: # TIME[s] SPEED[MB/s] rfc3174 2.207 27.65 rfc3174 2.21 27.62 linus 1.022 59.74 linusas 1.058 57.7 linusas2 1.008 60.58 mozilla 2.485 24.56 mozillaas 2.522 24.2 openssl 0.6421 95.06 spelvin 0.5989 101.9 spelvina 0.6638 91.94 nettle 0.7132 85.58 # TIME[s] SPEED[MB/s] rfc3174 2.224 27.44 rfc3174 2.205 27.68 linus 0.9727 62.75 linusas 0.9766 62.5 linusas2 1.026 59.5 mozilla 2.52 24.22 mozillaas 2.547 23.96 openssl 0.6459 94.5 spelvin 0.6074 100.5 spelvina 0.6751 90.41 nettle 0.7254 84.14 so whatever differences there are between linus*, they seem to be in the noise, and the hand-scheduled asm beats all the C versions senseless. I'd like to get closer to the hand-tuned ones, but I don't see anything to do any more. It's all about gcc register choice and avoiding spilling. So compiler flags changing small details can have _huge_ differences in performance. Here's the Atom numbers with gcc given the "-Os" flag (just because I wanted to try): linus 1.072 56.94 linusas 0.9573 63.76 linusas2 0.9906 61.61 Why did 'linus' numbers go down? No idea. With -O3, it's the other way around: linus 0.9537 64 linusas 0.9566 63.8 linusas2 1.013 60.26 but again, there's variation enough that I'd probabyl need to run ten runs just to see how much is noise. But the "linusas2 sucks with -O3" is clear, as is the "linus sucks with -Os" thing. Very odd, and very random. Linus -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html