"P. Joshua Rovero" <rovero@sonalysts.com> writes:
>>> Ran sets of 150 pgbench runs, with clients (1, 2, 4, 8, 16) and
>>> transactions (5 each at 125, 250, 500, 1000, 2000, 4000),
>>
>> BTW, what was the pgbench "scale factor"?
> 1 for these cases.
Hm. You really want scale factor >= number of clients, else you will
mostly be measuring the effects of contention. The scale factor is the
same as the number of rows created in the "branches" table, and every
transaction wants to update one of the "branches" rows. So if you have
just one branch, all the clients try to update that same row every time,
effectively serializing their transactions.
I now suspect that what you measured is just some marginal improvement
we made in the lock manager. Not sure what, though.
regards, tom lane