Scott Marlowe wrote:
Have you tried running the memory stream benchmark Greg Smith had posted here a while back? It'll let you know if you're memory is bottlenecking. Right now my 48 core machines are the king of that benchmark with something like 70+Gig a second.
The big Opterons are still the front-runners here, but not with 70GB/s anymore. Earlier versions of stream-scaling didn't use nearly enough data to avoid L3 cache in the processors interfering with results. More recent tests I've gotten in done after I expanded the default test size for them show the Opterons normally hitting the same ~35GB/s maximum throughput that the Intel processors get out of similar DDR3/1333 sets. There are some outliers where >50GB/s still shows up. I'm not sure if I really believe them though; attempts to increase the test size now hit a 32-bit limit inside stream.c, and I think that's not really big enough to avoid L3 cache effects here.
In the table at https://github.com/gregs1104/stream-scaling the 4 X 6172 server is similar to Scott's system. I believe the results for 8 (37613) and 48 cores (32301) there. I remain somewhat suspicious that the higher reuslts of 40 - 51GB/s shown between 16 and 32 cores may be inflated by caching. At this point I'll probably need direct access to one of them to resolve this for sure. I've made a lot of progress with other people's servers, but complete trust in those particular results still isn't there yet.
-- Greg Smith 2ndQuadrant US greg@xxxxxxxxxxxxxxx Baltimore, MD PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.us "PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
