Re: [Xen-devel] Time went backwards

[Rik van Riel <riel@xxxxxxxxxx>]

On Sat, 11 Mar 2006, Keir Fraser wrote:
> On 10 Mar 2006, at 21:57, Rik van Riel wrote:
> 
> > stolen + blocked is larger than delta_cpu all the time:
> > 
> > Timer ISR/0: stolen 1636284 + blocked 109702879 > delta_cpu 108006671
> > printk: 33 messages suppressed.
> 
> Is sched_time > (processed_system_time + delta)? That would be the real
> killer.

Very frequently.  By significant amounts, too...

No, I have no idea why...

Timer ISR/0: stolen 1921037 + blocked 79704210 > delta_cpu 79978775
Timer ISR/0: sched_time 429620376038547 > delta 4006385 + cpu 
processed_system_time 429620356036193
Timer ISR/0: sched_time 429620710119143 > delta_cpu 206088604 + global 
processed_system_time 429620500036193
Timer ISR/0: sched_time 429621780039343 > delta 404013043 + cpu 
processed_system_time 429621360036193
Timer ISR/0: sched_time 429622284012371 > delta_cpu -11948 + global 
processed_system_time 429622280036193

> Because we only account stolen/blocked/running time in jiffy-sized chunks,
> it's possible for the three deltas to be out of sync with each other by a
> jiffy.

But we round everything down, so while it is possible for the
sum of rounded down stolen/blocked/running/idle to be way less
than the total, I don't see how the sum of these rounded down
values could ever be more than the total (which is only rounded
off once)...

-- 
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