Re: Reducing ClogControlLock contention

On 30 June 2015 at 08:22, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:

> This contention is masked by contention elsewhere, e.g. ProcArrayLock, so
> the need for testing here should come once other patches ahead of this are
> in.
>

Let me explain more clearly.

Andres' patch to cache snapshots and reduce ProcArrayLock was interesting,
but not initially compelling. We now have a solution that commits in
batches, which will reduce the number of times the ProcArray changes - this
will heighten the benefit from Andres' snapshot cache patch.

So the order of testing/commit should be

Queued commit patch
ProcArray cache patch
Clog shared commit patch (this one)

I didn't hear recent mention of Robert's chash patch, but IIRC it was
effective and so we hope to see it again soon also.

--
Simon Riggs http://www.2ndQuadrant.com/
<http://www.2ndquadrant.com/>
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services