On Tue, 2005-04-05 at 18:17, Andy Polyakov wrote: > > Current OpenSSL (0.9.8-dev) rc4speed throughput on a Nocona (Em64t, > > b4bit) 3.6GHz is 272Mb/s, while this version of RC4 code can archive > > 536Mb/s in RC4Speed. > > > > ããWould you please review it? > > Cool conditional moves in unrolled loop. Have you considered/tried cmov > instead of jump over move instuction? No, there is no conditional move > with zero extention, but upper part is maintained zeroed, so that byte > cmov shoud do... Well, I bet those jumps are seldom taken, so that > branch prediction logic can make better job than cmov, but I have to ask:-) > Well, I tried use cmov here, it just slow down the throughput a lot... > Or how about moving mozb (%rdi,%r10),%r8d upwards as movzb > (%rdi,%r10),%r14b and make inter-register move between r8 and r14 > conditional? > I will try it. > The reason I didn't attempt to unroll the RC4_CHAR loop was that I never > had access to EM64T hardware and simply mechanically ported P4 loop from > 32-bit implementation [where unrolling affected performance negatively] > and tested it for correctness on Opteron. > > BTW, 272MBps at 3.6GHz? I get 262MBps out of [as just mentioned > virtually identical] 32-bit code at 2.4GHz P4... A. > In fact, Your implement on EM64t isn't that slow if we change the inc and dec to add and sub. :)
With that change the throughput boost from 272Mb/s to 396Mb/s. I have not investigated the 32 bit P4 path yet, But you should see performance gain on P4 with this change. Zou Nan hai ______________________________________________________________________ OpenSSL Project http://www.openssl.org Development Mailing List [email protected] Automated List Manager [EMAIL PROTECTED]
