Re: 8.3 synchronous_commit

On Mon, 21 Jan 2008, Jeff Davis wrote:

> He was referring to the CFQ I/O scheduler. I don't think that will
> affect pgbench itself, because it doesn't read/write to disk, right?

It does if you are writing latency log files but it shouldn't be in the 
cases given.  But there's something weird about the interplay between the 
server disk I/O under CFQ and the time slices the pgbench client gets when 
they're all on the same system.  pgbench is certainly a badly scaling (in 
regards to how it handles simulating many clients) single process utility 
and anything that starves its execution sometimes is deadly.  I never dug 
deep into the exact scheduler issues, but regardless in this case it's 
kind of unrealistic for Hannes to expect to simulate 100 clients on a 
small system and still get a true view of how the server on that system 
performs.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD