lkml.org 
[lkml]   [2014]   [Jan]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 tip/core/timers 0/5] Crude timer-wheel latency hacks
On Wed, Jan 15, 2014 at 08:02:03PM -0800, Paul E. McKenney wrote:
> Hello!
>
> The following five patches provide some crude timer-wheel latency patches.
> I understand that a more comprehensive solution is in progress, but in the
> meantime, these patches work well in cases where a given CPU has either
> zero or one timers pending, which is a common case for NO_HZ_FULL kernels.
> Note that these patches do not help in the case where a given timer wheel
> has a pair of widely separated timers, while the more comprehensive
> solution is likely to handle more gracefully. So, on the off-chance
> that this is helpful to someone, the individual patches are as follows:
>
> 1. Add ->all_timers field to tbase_vec to count all timers, not
> just the non-deferrable ones.
>
> 2. Avoid jiffy-at-a-time stepping when the timer wheel is empty.
>
> 3. Avoid jiffy-at-a-time stepping when the timer wheel transitions
> to empty.
>
> 4. Avoid jiffy-at-a-time stepping after a timer is added to an
> initially empty timer wheel.
>
> 5. Make internal_add_timer() update ->next_timer if ->active_timers == 0,
> courtesy of Oleg Nesterov.

They seem like perfectly fine bandaids ;-)

Acked-by: Peter Zijlstra <peterz@infradead.org>


\
 
 \ /
  Last update: 2014-01-16 17:01    [W:0.067 / U:0.024 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site