Re: kqueue

On Thu, Apr 21, 2016 at 3:31 PM, Alvaro Herrera
<alvherre(at)2ndquadrant(dot)com> wrote:
> Robert Haas wrote:
>> On Thu, Apr 21, 2016 at 2:22 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> > On 2016-04-21 14:15:53 -0400, Robert Haas wrote:
>> >> On Tue, Mar 29, 2016 at 7:53 PM, Thomas Munro
>> >> <thomas(dot)munro(at)enterprisedb(dot)com> wrote:
>> >> > On the WaitEventSet thread I posted a small patch to add kqueue
>> >> > support[1]. Since then I peeked at how some other software[2]
>> >> > interacts with kqueue and discovered that there are platforms
>> >> > including NetBSD where kevent.udata is an intptr_t instead of a void
>> >> > *. Here's a version which should compile there. Would any NetBSD
>> >> > user be interested in testing this? (An alternative would be to make
>> >> > configure to test for this with some kind of AC_COMPILE_IFELSE
>> >> > incantation but the steamroller cast is simpler.)
>> >>
>> >> Did you code this up blind or do you have a NetBSD machine yourself?
>> >
>> > RMT, what do you think, should we try to get this into 9.6? It's
>> > feasible that the performance problem 98a64d0bd713c addressed is also
>> > present on free/netbsd.
>>
>> My personal opinion is that it would be a reasonable thing to do if
>> somebody can demonstrate that it actually solves a real problem.
>> Absent that, I don't think we should rush it in.
>
> My first question is whether there are platforms that use kqueue on
> which the WaitEventSet stuff proves to be a bottleneck. I vaguely
> recall that MacOS X in particular doesn't scale terribly well for other
> reasons, and I don't know if anybody runs *BSD in large machines.
>
> On the other hand, there's plenty of hackers running their laptops on
> MacOS X these days, so presumably any platform dependent problem would
> be discovered quickly enough. As for NetBSD, it seems mostly a fringe
> platform, doesn't it? We would discover serious dependency problems
> quickly enough on the buildfarm ... except that the only netbsd
> buildfarm member hasn't reported in over two weeks.
>
> Am I mistaken in any of these points?
>
> (Our coverage of the BSD platforms leaves much to be desired FWIW.)

My impression is that the Linux problem only manifested itself on
large machines. I might be wrong about that. But if that's true,
then we might not see regressions on other platforms just because
people aren't running those operating systems on big enough hardware.

--
Robert Haas
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