Re: Excessive context switching on SMP Xeons

Here's a few numbers from the Opteron 250.  If I get some time I'll post
a more comprehensive comparison including some other systems.

The system is a Sun v20z.  Dual Opteron 250, 2.4Ghz, Linux 2.6, 8 GB
memory.   I did a compile and install of pg 8.0 beta 3.  I created a
data base on a tmpfs file system and ran pgbench.  Everything was "out
of the box", meaning I did not tweak any config files.

I used this for pgbench:
$ pgbench -i -s 32

and this for pgbench invocations:
$ pgbench -s 32 -c 1 -t 10000 -v


clients      tps
1            1290
2            1780
4            1760
8            1680
16           1376
32            904


How are these results useful?  In some sense, this is a speed of light
number for the Opteron 250.   You'll never go faster on this system with
a real storage subsystem involved instead of a tmpfs file system.   It's
also a set of numbers that anyone else can reproduce as we don't have to
deal with any differences in file systems, disk subsystems, networking,
etc.   Finally, it's a set of results that anyone else can compute on
Xeon's or other systems and make a simple (and naive) comparisons.


Just to stay on topic:   vmstat reported about 30K cs / second while
this was running the 1 and 2 client cases.

-- Alan