| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Васильев Дмитрий <d(dot)vasilyev(at)postgrespro(dot)ru>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Performance degradation in commit ac1d794 |
| Date: | 2016-03-17 14:57:04 |
| Message-ID: | 20160317145704.hagephye6yo4jgq3@alap3.anarazel.de |
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| Thread: | |
| Lists: | pgsql-hackers |
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
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