On Wed, Aug 18, 2010 at 1:25 PM, Yeb Havinga <yebhavinga@xxxxxxxxx> wrote: > Samuel Gendler wrote: >> >> When running pgbench on a db which fits easily into RAM (10% of RAM = >> -s 380), I see transaction counts a little less than 5K. When I go to >> 90% of RAM (-s 3420), transaction rate dropped to around 1000 ( at a >> fairly wide range of concurrencies). At that point, I decided to >> investigate the performance impact of write barriers. > > At 90% of RAM you're probable reading data as well, not only writing. > Watching iostat -xk 1 or vmstat 1 during a test should confirm this. To find > the maximum database size that fits comfortably in RAM you could try out > http://github.com/gregs1104/pgbench-tools - my experience with it is that it > takes less than 10 minutes to setup and run and after some time you get > rewarded with nice pictures! :-) Yes. I've intentionally sized it at 90% precisely so that I am reading as well as writing, which is what an actual production environment will resemble. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
