Re: kvm guest: hrtimer: interrupt too slow

[Michael Tokarev <mjt@tls.msk.ru>]

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)

[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.

> It's not swapping.  Swapping is in a separate table, with columns titled
> pswpin/s and pswpout/s -- first table.
> 
> On my home machine with no swap at all, 4gig memory and 2gig free,
> pgpgin and pgpgout are increasing too.
> 
> Also, while in the second case (21:46:56) there's actually some
> noticeable activity (page faults at least), in first case that
> activity is modest.
> 
> Note there's no documentation for /proc/vmstat file :)
> 
> /mjt