Re: Performance degradation in commit ac1d794

On Thu, Jan 14, 2016 at 12:14 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2016-01-14 12:07:23 -0500, Robert Haas wrote:
>> > Do we want to provide a backward compatible API for all this? I'm fine
>> > either way.
>>
>> How would that work?
>
> I'm thinking of something like;
>
> int WaitOnLatchSet(LatchEventSet *set, int wakeEvents, long timeout);
>
> int
> WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,long timeout)
> {
> LatchEventSet set;
>
> LatchEventSetInit(&set, latch);
>
> if (sock != PGINVALID_SOCKET)
> LatchEventSetAddSock(&set, sock);
>
> return WaitOnLatchSet(set, wakeEvents, timeout);
> }
>
> I think we'll need to continue having wakeEvents and timeout parameters
> for WaitOnLatchSet, we quite frequently want to wait socket
> readability/writability, not wait on the socket, or have/not have
> timeouts.

Well, if we ever wanted to support multiple FDs, we'd need the
readability/writeability thing to be per-fd, not per-set.

Overall, if this is what you have in mind for backward compatibility,
I rate it M for Meh. Let's just break compatibility and people will
have to update their code. That shouldn't be hard, and if we don't
make people do it when we make the change, then we'll be stuck with
the backward-compatibility interface for a decade. I doubt it's worth
it.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company