Re: Cost of XLogInsert CRC calculations

On E, 2005-05-16 at 12:35 -0400, Tom Lane wrote:

> Given the lack of impressive advantage to the 64-bit code even on 64-bit
> architectures, it might be best to go with the 32-bit code everywhere,
> but I also think we have grounds to file a gcc bug report.

Maybe on other platforms , but 20% on Power is not something we should
throw away.

crc32 compiled as 32bit executable is 10% slower than crc64 as eithet 32
or 64 bit exe, but if you compile your backend as 64bit then the
difference is almost 20%. crc64 is the same speed compiled either way.

gcc version 3.4.3 20041212 (Red Hat 3.4.3-9.EL4)
on OpenPower5 1.8GHz

file ./crctest
./crctest: ELF 32-bit MSB executable, PowerPC or cisco 4500, version 1
(SYSV)
cc -O1 crctest.c -o crctest -- time 0.584327 s
cc -O2 crctest.c -o crctest -- time 0.594664 s
cc -O3 crctest.c -o crctest -- time 0.594764 s

file ./crctest
./crctest: ELF 64-bit MSB executable, cisco 7500, version 1 (SYSV)
cc -O1 -m64 crctest.c -o crctest -- time 0.644473 s
cc -O2 -m64 crctest.c -o crctest -- time 0.648033 s
cc -O3 -m64 crctest.c -o crctest -- time 0.688682 s

file ./crctest64
./crctest64: ELF 64-bit MSB executable, cisco 7500, version 1 (SYSV)
cc -O1 -m64 crctest64.c -o crctest64 -- time 0.545026 s
cc -O2 -m64 crctest64.c -o crctest64 -- time 0.545470 s
cc -O3 -m64 crctest64.c -o crctest64 -- time 0.545037 s

file ./crctest64
./crctest64: ELF 32-bit MSB executable, PowerPC or cisco 4500, version 1
(SYSV)
cc -O1 crctest64.c -o crctest64 -- time 0.545364 s
cc -O2 crctest64.c -o crctest64 -- time 0.644093 s
cc -O3 crctest64.c -o crctest64 -- time 0.644155 s

> Anyone want to try it with non-gcc compilers? I attach a slightly
> cleaned-up version of Mark's original (doesn't draw compiler warnings
> or errors on what I tried it on).

I'll probably get a chance to try IBM's own compiler tomorrow

--
Hannu Krosing <hannu(at)skype(dot)net>