bug#51734: 29.0.50; got slow

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 11 Nov 2021 15:30:51 -0500
> Cc: yamaoka@jpl.org, 51734@debbugs.gnu.org
> From: Ken Brown <kbrown@cornell.edu>
> 
> >> Here's a patch that does that.  Does it look OK?
> > 
> > ENOPATCH
> 
> Sorry.
> 
> From abe88311b7e47c1cdac2b2405d43ff19826fd911 Mon Sep 17 00:00:00 2001
> From: Ken Brown <kbrown@cornell.edu>
> Date: Thu, 11 Nov 2021 15:09:24 -0500
> Subject: [PATCH] Don't start both timerfd and alarms on Cygwin
> 
> * src/atimer.c (set_alarm) [CYGWIN]: Don't start both timerfd and
> alarms; this causes a slowdown.  (Bug#51734)
> ---
>  src/atimer.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/src/atimer.c b/src/atimer.c
> index 490c21bff1..9bde9c2446 100644
> --- a/src/atimer.c
> +++ b/src/atimer.c
> @@ -316,6 +316,13 @@ set_alarm (void)
>  	      exit = true;
>  	    }
>  # endif
> +
> +# ifdef CYGWIN
> +	  /* Don't start both timerfd and alarms on Cygwin; this
> +	     causes a slowdown (bug#51734). */
> +	  if (exit)
> +	    return;
> +# endif
>  	  if (alarm_timer_ok
>  	      && timer_settime (alarm_timer, TIMER_ABSTIME, &ispec, 0) == 0)
>  	    exit = true;
> -- 

LGTM, thanks.  It would be good to understand why starting alarms
causes slowdown on Cygwin, though.