From: | Greg Smith <gsmith(at)gregsmith(dot)com> |
---|---|
To: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
Cc: | Merlin Moncure <mmoncure(at)gmail(dot)com>, Dave Youatt <dave(at)meteorsolutions(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: hyperthreaded cpu still an issue in 8.4? |
Date: | 2009-07-28 23:21:24 |
Message-ID: | alpine.GSO.2.01.0907281905040.1670@westnet.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-performance |
On Tue, 28 Jul 2009, Scott Marlowe wrote:
> Just FYI, I ran the same basic test but with -c 10 since -c shouldn't
> really be greater than -s
That's only true if you're running the TPC-B-like or other write tests,
where access to the small branches table becomes a serious hotspot for
contention. The select-only test has no such specific restriction as it
only operations on the big accounts table. Often peak throughput is
closer to a very small multiple on the number of cores though, and
possibly even clients=cores, presumably because it's more efficient to
approximately peg one backend per core rather than switch among more than
one on each--reduced L1 cache contention etc. That's the behavior you
measured when your test showed better results with c=10 than c=16 on a 8
core system, rather than suffering less from the "c must be < s"
contention limitation.
Sadly I don't have or expect to have a W5580 in the near future though,
the X5550 @ 2.67GHz is the bang for the buck sweet spot right now and
accordingly that's what I have in the lab at Truviso. As Merlin points
out, that's still plenty to spank any select-only pgbench results I've
ever seen. The multi-threaded pgbench batch submitted by Itagaki Takahiro
recently is here just in time to really exercise these new processors
properly.
--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD
From | Date | Subject | |
---|---|---|---|
Next Message | Scott Marlowe | 2009-07-28 23:23:29 | Re: hyperthreaded cpu still an issue in 8.4? |
Previous Message | Scott Carey | 2009-07-28 22:52:47 | Re: hyperthreaded cpu still an issue in 8.4? |