Re: New to PostgreSQL, performance considerations

Hi,

Did someone try '-mfpmath=sse -msse3'?

Would be interesting to know if -mfpmath=sse boost the performance.

I guess, the difference in the generated code isn't that much between
i686 and prescott. The bigger step is i386 to i686. '-mfpmath=sse
-msse3' will also use the SSE unit, which the classic i686 doesn't have.

CFLAGS=-O2 -march=prescott -mfpmath=sse -msse3

Best regards
Sven.

Daniel van Ham Colchete schrieb:
> I just made another test with a second Gentoo machine:
>
> Pentium 4 3.0Ghz Prescott
> GCC 4.1.1
> Glibc 2.4
> PostgreSQL 8.1.5
> Kernel 2.6.17
>
> Same postgresql.conf as yesterday's.
>
> First test
> ==========
> GLIBC: -O2 -march=i686
> PostgreSQL: -O2 -march=i686
> Results: 974.638731 975.602142 975.882051 969.142503 992.914167
> 983.467131 983.231575 994.901330 970.375221 978.377467
> Average (error): 980 tps (13 tps)
>
> Second test
> ===========
> GLIBC: -O2 -march=i686
> PostgreSQL: -O2 -march=prescott
> Results: 988.319643 976.152973 1006.482553 992.431322 983.090838
> 992.674065 989.216746 990.897615 987.129802 975.907955
> Average (error): 988 tps (15 tps)
>
> Third test
> ==========
> GLIBC: -O2 -march=prescott
> PostgreSQL: -O2 -march=i686
> Results: 969.085400 966.187309 994.882325 968.715150 956.766771
> 970.151542 960.090571 967.680628 986.568462 991.756520
> Average (error): 973 tps (19 tps)
>
> Forth test
> ==========
> GLIBC: -O2 -march=prescott
> PostgreSQL: -O2 -march=prescott
> Results: 980.888371 978.128269 969.344669 978.021509 979.256603
> 993.236457 984.078399 981.654834 976.295925 969.796277
> Average (error): 979 tps (11 tps)
>
> The results showed no significant change. The conclusion of today's
> test would be that there are no improvement at PostgreSQL when using
> -march=prescott.
>
> I only see 3 diferences between yesterday's server and today's: the
> kernel version (y: 2.6.18, t:2.6.17), the server uses an IDE harddrive
> (yesterday was SATA), and the gcc version (3.4.6 -> 4.1.1).
>
> I don't know why yesterday we had improved and today we had not.
>
> Best
> Daniel
>
> On 12/12/06, Daniel van Ham Colchete <daniel(dot)colchete(at)gmail(dot)com> wrote:
>> I'm making some other tests here at another hardware (also Gentoo). I
>> found out that PostgreSQL stops for a while if I change the -t
>> parameter on bgbench from 600 to 1000 and I have ~150 tps instead of
>> ~950tps.