I have been running the nbench-byte-2.1 benchmark on a
mips r4k processor with various combinations of kernel
and distribution packages. I initially started with a
2.4.2 kernel using the redhat 5.1 distribution found
on the SGI mips site. I compiled nbench native on the
target with redhat mounted via nfs. I used this as my
base.
I then ran a 2.4.6 kernel on the same mips 4k
processor, but this time with the redhat 7.0
distribution. I compiled native using the
distributions compiler. This resulted in :
a 3 % reduction in the Memory Index benchmark
a 2 % increase in the Integer Index benchmark
a 23 % reduction in the Floating Point Index benchmark
Using the same 2.4.6 kernel on the same mips 4k
processor, with the redhat 7.1 distribution (compiling
native with the distribution's compiler ) I got :
a 5.7 % reduction in the Memory Index benchmark
a 1.5 % reduction in the Integer Index benchmark
a 27 % reduction in the Floating point Index benchmark
Also as a test I ran the redhat 5.1 native compiled
nbench executable on the 2.4.6 / redhat 7.0 setup and
again saw reduced performance :
a 4.8 % reduction in the Memory Index benchmark
a 1.5 % increase in the Integer Index benchmark
a 26 % reduction in the floating point benchmark
Although I tried various compiler switches to acheive
the highest index I could on a per kernel / per
distribution basis ( they weren't always the same ).
My basic CFLAGS settings were :
CFLAGS = -s -static -Wall -O2 -fomit-frame-pointer
-funroll-all-loops -mips2 -finline-functions.
>From the above tests it seems that newer does not in
fact mean faster. I can only speculate as to why, and
so I would appreciate hearing from anyone who :
a, has suggestions on how to optimize compiler
performance.
b, may know why performance seems to degrade with a
newer kernel and with a newer distribution ? newer
compiler ?
c, any other tips for improving kernel / application
performance.
Wayne
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