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