timerfd question

Corinna Vinschen corinna-cygwin@cygwin.com
Fri Nov 12 09:41:10 GMT 2021

On Nov 11 17:52, Ken Brown wrote:
> This question is almost certainly too vague to be answerable, but I'll try
> anyway.  Is there any obvious reason that it's bad to have two timers
> running simultaneously, one using timerfd (started via timerfd_settime) and
> one using a POSIX timer (started via timer_settime)?

They don't share code, nor threads.  I don't see a reason they should
influence each other.  Both are starting timers and handle them
in independent threads.

> Here's the context: Emacs runs timers.  Until recently it used timerfd if
> available, and otherwise a POSIX timer.  After a recent change, it starts
> both kinds of timers.  This causes a severe slowdown on Cygwin
> (https://debbugs.gnu.org/cgi/bugreport.cgi?bug=51734#32).  The easiest thing
> is just to disable that change on Cygwin, but I'd feel better understanding
> why this is a problem.

A STC might be helpful.


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