Re: [PATCH -rt] timer: upper bound on loops of __run_timers processing

Re: [PATCH -rt] timer: upper bound on loops of __run_timers processing

[Marcelo Tosatti]

Ping?

On Tue, Dec 30, 2014 at 05:52:28PM -0200, Marcelo Tosatti wrote:
> 
> Commit "timers: do not raise softirq unconditionally", allows for timer
> wheel processing (__run_timers) to be delayed for long periods of time.
> 
> The effect is that 
> 
> loops = jiffies - base->timer_jiffies
> 
> Can grow to very large values resulting in __run_timers taking hundreds
> of milliseconds to execute.
> 
> Fix by creating an upper bound on the number of loops to be processed.
> This allows a nohz=off kernel to achieve desired latencies.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> diff --git a/kernel/timer.c b/kernel/timer.c
> index f59e18c..c128416 100644
> --- a/kernel/timer.c
> +++ b/kernel/timer.c
> @@ -1488,6 +1488,12 @@ void run_local_timers(void)
>  	}
>  #endif
>  
> +	if (time_after_eq(jiffies, base->timer_jiffies)) {
> +		unsigned long jiffies_delta = jiffies - base->timer_jiffies;
> +		if (jiffies_delta > TVR_SIZE)
> +			raise_softirq(TIMER_SOFTIRQ);
> +	}
> +
>  	if (!base->active_timers)
>  		goto out;
>  

Re: [PATCH -rt] timer: upper bound on loops of __run_timers processing

[Steven Rostedt]

On Wed, 14 Jan 2015 15:21:47 -0200
Marcelo Tosatti <mtosatti@redhat.com> wrote:

> 
> Ping?
> 

Sorry, I've fallen behind since the holidays and still trying to catch
up. I'll try to look at this this week.

-- Steve

> On Tue, Dec 30, 2014 at 05:52:28PM -0200, Marcelo Tosatti wrote:
> > 
> > Commit "timers: do not raise softirq unconditionally", allows for timer
> > wheel processing (__run_timers) to be delayed for long periods of time.
> > 
> > The effect is that 
> > 
> > loops = jiffies - base->timer_jiffies
> > 
> > Can grow to very large values resulting in __run_timers taking hundreds
> > of milliseconds to execute.
> > 
> > Fix by creating an upper bound on the number of loops to be processed.
> > This allows a nohz=off kernel to achieve desired latencies.
> > 
> > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> > 
> > diff --git a/kernel/timer.c b/kernel/timer.c
> > index f59e18c..c128416 100644
> > --- a/kernel/timer.c
> > +++ b/kernel/timer.c
> > @@ -1488,6 +1488,12 @@ void run_local_timers(void)
> >  	}
> >  #endif
> >  
> > +	if (time_after_eq(jiffies, base->timer_jiffies)) {
> > +		unsigned long jiffies_delta = jiffies - base->timer_jiffies;
> > +		if (jiffies_delta > TVR_SIZE)
> > +			raise_softirq(TIMER_SOFTIRQ);
> > +	}
> > +
> >  	if (!base->active_timers)
> >  		goto out;
> >  

Re: [PATCH -rt] timer: upper bound on loops of __run_timers processing

[Marcelo Tosatti]

Ping ?

On Wed, Jan 14, 2015 at 03:21:47PM -0200, Marcelo Tosatti wrote:
> 
> Ping?
> 
> On Tue, Dec 30, 2014 at 05:52:28PM -0200, Marcelo Tosatti wrote:
> > 
> > Commit "timers: do not raise softirq unconditionally", allows for timer
> > wheel processing (__run_timers) to be delayed for long periods of time.
> > 
> > The effect is that 
> > 
> > loops = jiffies - base->timer_jiffies
> > 
> > Can grow to very large values resulting in __run_timers taking hundreds
> > of milliseconds to execute.
> > 
> > Fix by creating an upper bound on the number of loops to be processed.
> > This allows a nohz=off kernel to achieve desired latencies.
> > 
> > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> > 
> > diff --git a/kernel/timer.c b/kernel/timer.c
> > index f59e18c..c128416 100644
> > --- a/kernel/timer.c
> > +++ b/kernel/timer.c
> > @@ -1488,6 +1488,12 @@ void run_local_timers(void)
> >  	}
> >  #endif
> >  
> > +	if (time_after_eq(jiffies, base->timer_jiffies)) {
> > +		unsigned long jiffies_delta = jiffies - base->timer_jiffies;
> > +		if (jiffies_delta > TVR_SIZE)
> > +			raise_softirq(TIMER_SOFTIRQ);
> > +	}
> > +
> >  	if (!base->active_timers)
> >  		goto out;
> >  
> --
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Re: [PATCH -rt] timer: upper bound on loops of __run_timers processing

[Sebastian Andrzej Siewior]

* Marcelo Tosatti | 2015-01-26 19:12:31 [-0200]:

>Ping ?

please resent.

Sebastian