Re: kvm guest: hrtimer: interrupt too slow

[Frederic Weisbecker <fweisbec@gmail.com>]

On Sat, Oct 10, 2009 at 01:18:16PM +0400, Michael Tokarev wrote:
> Michael Tokarev wrote:
>> Frederic Weisbecker wrote:
> []
>>>>> Was there swapping going on?
>>>> Not as far as I can see, and sar output agrees.
>>>
>>> But I can read this from you guest traces:
>
> I missed this one yesterday.  Note it's GUEST traces
> indeed.  Higher (read: non-zero) pgp{in,out} and faults
> values happens in *guest*, not on host (original question
> was if we've swapping in HOST, which'd explain the timer
> issues)



Yeah indeed. But still, that's a strange happenstance.



> [cutting extra all-zero columns]
>>>                 pgpgin/s pgpgout/s   fault/s  pgfree/s
>>> 11:44:47         0.00     32.32    907.07       277.78
>>> 11:44:48        27.59     22.99     44.83       150.57
>>> 11:44:49         0.00     33.68     22.11       218.95
>>> [...]
>>> 21:46:54         0.00     31.68     16.83        90.10
>>> 21:46:55         0.00    108.00     17.00        89.00
>>> 21:46:56         9.76    482.93   3890.24       439.02
>>> 21:46:57         0.00    760.00   8627.00      1133.00
>>> 21:46:58         0.00     84.85   2612.12       138.38
>>> 21:46:59         0.00     16.00     17.00        90.00
>>>
>>> So it looks like there was some swapping in when the hrtimer (spuriously)
>>> hanged.
>
> One possible guess.  Since the guest hanged for some time, the
> higher values there might be a result of accumulated values for
> several seconds.



May be yeah. I don't know enough about virtual internals so...