Re: [PATCH v2 0/3] Deferrable timers support for timerfd API

From: Alexey Perevalov
Date: Wed Feb 05 2014 - 01:44:02 EST

On 02/04/2014 08:10 PM, Thomas Gleixner wrote:
On Mon, 27 Jan 2014, Alexey Perevalov wrote:
On 01/21/2014 11:12 PM, John Stultz wrote:
Thomas: Any thought here? Should we be trying to unify the timerfd flags
and the posix timer flags (specifically things like TIMER_CANCEL_ON_SET,
which is currently timerfd-only)? Should a deferrable flag be added to
the hrtimer core or left to the timer wheel?
The timer cancel on set was added only to timerfd because timerfd is a
non posix interface and we are halfways free to add stuff to
it. Adding extra flags to the real posix timer interfaces is a
different story.
And what about "deferrable" possibility for hrtimers, do you consider it reasonable?

What's the rationale for a deferrable flag for user space interfaces?
The main reason of this was do not call user space timers on system idle, to safe power on embedded systems, especially in case of NOHZ.



Best regards,
Alexey Perevalov
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