[PERFORM] Practical upper limits of pgbench read/write tps with 8.3

I'm spending a third day testing with the ioDrive, and it occurred to
me that I should normalize my tests by mounting the database on a
ramdisk. The results were surprisingly low. On the single 2.2GHz
Athlon, the maximum tps seems to be 1450. This is achieved with a
single connection. I/O rates to and from the ramdisk never exceed
50MB/s on a one-minute average.

With the flash device on the same benchmark, the tps rate is 1350,
meaning that as far as PostgreSQL is concerned, on this machine, the
flash device achieves 90% of the best possible performance.

Question being: what's the bottleneck? Is PG lock-bound?

-jwb

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