Re: Query execution in Perl TAP tests needs work

On Wed, Aug 30, 2023 at 09:48:42AM +1200, Thomas Munro wrote:
> On Wed, Aug 30, 2023 at 1:49 AM Noah Misch <noah@leadboat.com> wrote:
> > On Tue, Aug 29, 2023 at 04:25:24PM +1200, Thomas Munro wrote:
> > > On Tue, Aug 29, 2023 at 1:48 PM Noah Misch <noah@leadboat.com> wrote:
> > > > https://github.com/cpan-authors/IPC-Run/issues/166#issuecomment-1288190929
> > >
> > > Interesting.  But that shows a case with no pipes connected, using
> > > select() as a dumb sleep and ignoring SIGCHLD.  In our usage we have
> > > pipes connected, and I think select() should return when the child's
> > > output pipes become readable due to EOF.  I guess something about that
> > > might be b0rked on Windows?  I see there is an extra helper process
> > > doing socket<->pipe conversion (hah, that explains an extra ~10ms at
> > > the start in my timestamps)...
> >
> > In that case, let's assume it's not the same issue.
> 
> Yeah, I think it amounts to the same thing, if EOF never arrives.
> 
> I suspect that we could get ->safe_psql() down to about ~25ms baseline
> if someone could fix the posited IPC::Run EOF bug

I pushed optimizations in https://github.com/cpan-authors/IPC-Run/pull/172
that make the TAP portion of "make check-world" 7% faster on my GNU/Linux
machine.  I didn't confirm an EOF bug, but that change also reduces Windows
idle time in simple tests.  I didn't run Windows check-world with it.  For
non-Windows, we can get almost all the benefit from the attached one-liner.
(The relative benefit is probably lower for parallel check-world, where idle
threads matter less, and for slower machines.)