Re: [RFC,PATCH] Avoid manual shift-and-test logic in AllocSetFreeIndex

Hi,

> Also, are you still seeing the same improvement with the __builtin_clz 
> as your inline asm implementation?

In my benchmark program, it is a little different performance
in fls implementation and inline asm implementation.
However, the result of a pgbench is almost the same improvement.

Here is the result of my benchmark.

Xeon(Core architecture) bytes     :     4     8    16    32    64   128   256   512  1024   mix original  : 0.780 0.790
0.8200.870 0.930 0.980 1.040 1.080 1.140 0.910 inline asm: 0.320 0.180 0.190 0.180 0.190 0.180 0.190 0.180 0.190 0.170
fls      : 0.270 0.260 0.290 0.290 0.290 0.290 0.290 0.300 0.290 0.380
 

Xeon(P4 architecrure) bytes     :     4     8    16    32    64   128   256   512  1024   mix original  : 0.520 0.520
0.6700.780 0.950 1.000 1.060 1.190 1.250 0.940 inline asm: 0.610 0.530 0.530 0.520 0.520 0.540 0.540 0.580 0.540 0.600
fls      : 0.390 0.370 0.780 0.780 0.780 0.790 0.780 0.780 0.780 0.520
 


pgbench result (measured by oprofile)

CPU: Xeon(P4 architecrure)
test program: pgbench -c 1 -t 50000 (fsync=off)

original
samples  %        symbol name
66854     6.6725  AllocSetAlloc
11817     1.1794  AllocSetFree

inline asm
samples  %        symbol name
47610     4.9333  AllocSetAlloc
6248      0.6474  AllocSetFree

fls
samples  %        symbol name
48779     4.9954  AllocSetAlloc
7648      0.7832  AllocSetFree

Best regards,

---
Atsushi Ogawa