Re: [PATCH] prctl: Add PR_SET_TIMERSLACK_PID for setting timer slack of an arbitrary thread.

[Arjan van de Ven]

> > and most of the RT guys would only tolerate a little bit of it
> >
> > is there any real/practial use of going longer than 4 seconds? if there
> > is then yeah fixing it makes sense.
> > if it's just theoretical... shrug... 32 bit systems have a bunch of
> > other limits/differences a well.
>
> So I'd think it would be mostly theoretical, but in my testing on a
> VM, setting the timerslack for bash to 10 secs made time sleep 1 take
> ~10.5 seconds. So its apparently not too hard to coalesce fairly far
> out (I need to spend a bit more time to verify that events really
> weren't happening during that time and we're not just doing
> unnecessary delays with the extra slack).

99% sure you're hitting something else;
we look pretty much only 1 ahead in the queue for timers to run to see if
they can be run, once we hit a timer that's not ready yet we stop.
your 10 second ahead is behind a whole bunch of other not-ready ones
so won't even be looked at until its close


> But yea. My main concern is that if we do a consistent 64bit interface
> for all arches in the /proc/<pid>/timerslack_ns interface, it will
> make PR_GET_TIMERSLACK return incorrect results on 32bit systems when
> the slack is >= 2^32.

or we return UINT_MAX for that case. not too hard.