"Tom Lane" <tgl@sss.pgh.pa.us> writes:
> Gregory Stark <stark@enterprisedb.com> writes:
>> "Tom Lane" <tgl@sss.pgh.pa.us> writes:
>>> This patch implements Florian's idea about how to manage snapshot xmax
>>> without the ugly and performance-losing tactic of taking XidGenLock and
>>> ProcArrayLock at the same time. I had to do a couple of slightly klugy
>>> things to get bootstrap and prepared transactions to work, but on the
>>> whole it seems at least as clean as the code we have now. Comments?
>
>> Just that it will be fascinating to see what effects this has on the
>> benchmarks.
>
> Yeah, I was hoping to get some benchmarks before deciding whether it's
> worth the risk of pushing this into 8.3. I'm off trying pgbench now,
> but if anyone wants to try something more serious like DBT2 ...
I ran some DBT2 tests but haven't been able to show any performance effects
either in average or worst-case response times.
I think that's for a few reasons:
1) This is only a dual-processor machine I'm playing with and we scale well on
two processors already.
2) TPC-C doesn't have many read-only transactions
3) The deadlocks I found earlier cause enough noise in the response times to
hide any subtler effects.
We may have to wait until the next time Sun runs their 1,000-process monster
Java benchmark to see if it helps there.
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
