Re: Performance degradation in commit ac1d794

On Fri, Mar 18, 2016 at 1:34 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>
> 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?
>
> Which is important, because what's in what pfds[x] depends on
> wakeEvents. Folded it into a later patch; it's not harmful as long as
> we're only ever testing pfds[0].
>
>
> > 0003: Mostly boring. But the change to win32_latch.c seems to remove
> > an unrelated check.
>
> Argh.
>

+ * from inside a signal handler in latch_sigusr1_handler().

*

* Note: we assume that the kernel calls involved in drainSelfPipe()

* and SetLatch() will provide adequate synchronization on machines

* with weak memory ordering, so that we cannot miss seeing is_set if

* the signal byte is already in the pipe when we drain it.

*/

- drainSelfPipe();

-

Above part of comment looks redundant after this patch. I have done some
tests on Windows with 0003 patch which includes running the regressions
(vcregress check) and it passes. Will look into it tomorrow once again and
share if I find anything wrong with it, but feel to proceed if you want.

With Regards,
Amit Kapila.
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