lkml.org 
[lkml]   [2008]   [Dec]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] hrtimer: increase clock min delta threshold while interrupt hanging
On Sat, Dec 27, 2008 at 11:53:34AM +0100, Ingo Molnar wrote:
>
> * Frederic Weisbecker <fweisbec@gmail.com> wrote:
>
> > Impact: avoid hanging on slow systems
> >
> > While using the function graph tracer on a virtualized system, the
> > hrtimer_interrupt can hang the system on an infinite loop. This can be
> > caused on several situation where something intrusive is slowing the
> > system (ie: tracing) and the next clock events to program are always
> > before the current time. This patch implements a reasonable compromise.
> > If such a situation is detected, we share the CPUs time in 1/4 to
> > process the hrtimer interrupts. This is enough to let the system running
> > without serious starvation.
> >
> > It has been successfully tested under VirtualBox with 1000 HZ and 100 HZ
> > with function graph tracer launched. On both cases, the clock events
> > were increased until about 25 ms periodic ticks, which means 40 HZ.
> >
> > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > ---
> > kernel/hrtimer.c | 30 +++++++++++++++++++++++++++++-
> > 1 files changed, 29 insertions(+), 1 deletions(-)
>
> applied to tip/timers/hrtimers, thanks Frederic!


I will apply the comments that came along these reviews in a delta patch.
Note that I still wonder about false positive with a 5 loop check. I think
I will increase it to 10. This a more reasonable.

(I remember I had false positive but I'm not sure if that was because of early_printk
used for debugging. I didn't worry about it first, because I hadn't these false positive
on my last tests, just before I send this patch.)

>
> Thomas, any objections/observations?
>
> Ingo



\
 
 \ /
  Last update: 2008-12-27 15:13    [W:0.103 / U:0.460 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site