Re: WIP: bufmgr rewrite per recent discussions

Hi Tom,

I compiled and tested your patch on a dual Opteron server with 12GB RAM
running FC3. Here are the results I get with pgbench with a scale-factor of
10 over an average of 6 runs. All other postgresql.conf options were left at
their default values.

CVS tip results
---------------

Shared buffers = 1000
tps = 232.7013962 (including connections establishing)
tps = 250.9295233 (excluding connections establishing)

Shared buffers = 10000
tps = 217.7393482 (including connections establishing)
tps = 236.8184297 (excluding connections establishing)

Shared buffers = 100000
tps = 150.4182863 (including connections establishing)
tps = 178.3881158 (excluding connections establishing)

CVS tip + Tom's Bufmgr patch
----------------------------

Shared buffers = 1000
tps = 248.3239085 (including connections establishing)
tps = 270.0627257 (excluding connections establishing)

Shared buffers = 10000
tps = 249.7294955 (including connections establishing)
tps = 273.6144427 (excluding connections establishing)

Shared buffers = 100000
tps = 197.8116898 (including connections establishing)
tps = 224.362671 (excluding connections establishing)

The interesting thing to note was that going up to 100000 buffers seemed to
cause the performance to go down again which is something I wouldn't have
expected on a server with such a large amount of RAM given that it was
suggested ARC would perform better with more shared buffers. But all in all,
it looks like your patch is having a positive effect on performance.

Kind regards,

Mark.

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