Re: [RFC] [PATCH 1/1] hrtimers: Cache next hrtimer

[Ashwin Chaugule]

Thomas Gleixner wrote:
> On Fri, 28 Aug 2009, Ashwin Chaugule wrote:
>   
> > Thomas Gleixner wrote:
> > Avg startup time 26.4 (10 runs) same as last run.
> >
> > total_calls is again equal to cache_hits ... Its been a while since I wrote my
> > patch. I'll need to look deeper to see if I've done something more. B)
> > Just to make sure, I ran my patch again, I clearly see cache_hits is always
> > less than total_calls.
> >     
>
> Hmm. I'd really like to know why that's behaving different. 
>
> Usually there are only timers in the CLOCK_MONOTONIC base during
> boot. CLOCK_REALTIME base should be empty most of the time. If my
> theory is correct then the number of reprogram events is correct as
> well because base[MONOTONIC]->first is always the one which armed the
> timer.
>
> Can you add some debug which tells us to which base the removed timer
> belongs ?
>   

You're right about that. I confirmed that its MONOTONIC all the way. (I didn't think it'd be like that)
However, the reason for different results, *I think* is coming from hrtimer_reprogram,
where we check if the newly enqueued timer is going to expire before the currently armed timer.
Thats where I change /next_hrtimer/ as well.

So, if the expires_next value is changed as a result of hrtimer_enqueue_reprogram, we just raise HRTIMER_SOFTIRQ (rightfully),
but the latest patch doesn't do those checks in this path, coz, we don't call force_reprogram. 


Cheers,
Ashwin


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/