More on 7.4b2 vs 7.3.4 performance

Josh Rovero wrote:

Per Tom Lane's suggestion, I increased the pgbench
scale factor to be equal to the max number of clients
in each test run.

Attached sample graph shows 1 - 10 clients,
100-500 transactions per client, with scale
factor=10 for all runs.

There is still a average 9% improvement in 7.4b2
transaction rates over 7.3.4. For low number
of clients (1 - 3) performance was almost the
same. For higher numbers of clients, the 7.4
advantage was often in the 15-25% range. Other
tests with scale factor == number of clients and
other pertubations gave similar results.
7.4 is almost always faster than 7.3.4.

Mind you now, I am *not* complaining.

That's closer to the performance improvement we were expecting.

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Josh Rovero <rovero@sonalysts.com> writes:

There is still a average 9% improvement in 7.4b2
transaction rates over 7.3.4. For low number
of clients (1 - 3) performance was almost the
same. For higher numbers of clients, the 7.4
advantage was often in the 15-25% range.

This seems more believable as a version-to-version improvement factor.

I suspect that your previous numbers reflect some isolated tweak that
we made in the lock management code, that happened to reduce the amount
of time wasted in a heavy-contention scenario. Not sure what though...

regards, tom lane