Re: Move PinBuffer and UnpinBuffer to atomics

On 2015-11-09 11:54:59 -0500, Jesper Pedersen wrote:
> Hi,
> 
> On 11/06/2015 03:47 PM, Jesper Pedersen wrote:
> >>Did you initdb between tests? Pgbench -i? Restart the database?
> >
> >I didn't initdb / pgbench -i between the tests, so that it is likely it.
> >
> 
> Each graph has a full initdb + pgbench -i cycle now.

That looks about as we'd expect: the lock-free pinning doesn't matter
and ssynchronous commit is beneficial. I think our bottlenecks in write
workloads are sufficiently elsewhere that it's unlikely that buffer pins
make a lot of difference.

You could try a readonly pgbench workload (i.e. -S), to see whether a
difference is visible there. For a pgbench -S workload it's more likely
that you only see significant contention on larger machines. If you've a
workload that touches more cached buffers, it'd be visible earlier.

> I know, I have a brown paper bag somewhere.

Why? This looks as expected, and the issues from the previous run were
easy to make mistakes?

Greetings,

Andres Freund