Re: Performance degradation in commit ac1d794

Hi,

On 2016-03-17 09:01:36 -0400, Robert Haas wrote:
> 0001: Looking at this again, I'm no longer sure this is a bug.
> Doesn't your patch just check the same conditions in the opposite
> order?

Yes, that's what's required

> 0004:
> 
> +         * drain it everytime WaitLatchOrSocket() is used. Should the
> +         * pipe-buffer fill up in some scenarios - widly unlikely - we're
> 
> every time
> wildly
> 
> Why is it wildly (or widly) unlikely?
> 
> The rejiggering this does between what is on which element of pfds[]
> appears to be unrelated to the ostensible purpose of the patch.

Well, not really. We need to know when to do drainSelfPipe(); Which gets
more complicated if pfds[0] is registered optionally.

I'm actually considering to drop this entirely, given the much heavier
rework in the WaitEvent set patch; making these details a bit obsolete.


Greetings,

Andres Freund