SMP scaling

On Tue, Mar 15, 2005 at 07:00:25PM -0500, Bruce Momjian wrote:
> Oh, you have to try CVS HEAD or a nightly snapshot. Tom made a major
> change that allows scaling in SMP environments.

Ok, I've done the tests comparing 8.0.1 against a snapshot from the 16th
and the results are impressive.
As well as the 16CPU Altix, I've done comparisons on two other 4CPU
machines which previously didn't scale as well as expected.

Clients 1 2 3 4 6 8 12 16 32 64
---------------------------------------------------------------------------------------
Altix pg-8.0.1 1.00 2.02 2.98 3.97 5.87 7.23 7.51 5.54 4.68 5.10
Altix pg-20050316 1.00 1.97 2.86 3.68 5.29 6.90 9.00 9.88 10.03 9.94
AMD64 pg-8.0.1 1.00 1.87 2.77 3.34 2.73 2.57 2.58 2.62
AMD64 pg-20050316 1.00 1.95 2.84 3.69 3.61 3.66 3.70 3.69
IA64 pg-8.0.1 1.00 1.97 2.91 3.82 2.91 2.92 2.94 2.98
IA64 pg-20050316 1.00 1.98 2.95 3.87 3.80 3.78 3.86 3.90

Altix == 16x 1.6GHz Itanium2 192GB memory
AMD64 == 4x 2.2GHz Opteron 848 8GB memory
IA64 == 4x 1.5GHz Itanium2 16GB memory

The altix still only scales up to 10x rather than 16x, but that probably
is the NUMA configuration taking effect now.
Also this machine isn't set up to run databases, so only has 1 FC I/O card,
which means a CPU can end up being 4 hops away from the memory and disk.

As the database is so small (8GB), relative to the machine, the data will
be on average 2 hops away. This gives an average of 72% of the speed of
local memory, based on previous measurements of speed vs hops.

So getting 63% of the theoretical maximum database throughput is pretty good.

-Mark