Re: write barrier question

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! :-)

regards,
Yeb Havinga