[Devel] [PATCH rh7] ve: Add interface for @start_timespec and @real_start_timespec adjustmen

[Pavel Emelyanov]

On 02/09/2016 02:25 PM, Cyrill Gorcunov wrote:
> On Tue, Feb 09, 2016 at 02:14:25PM +0300, Vladimir Davydov wrote:
>>>
>>> It was named so in pcs6, so I tried to preserve naming. But sure I
>>> can rename, that's not a problem.
>>
>> I mean not ve_struct.start_timespec - its name is perfectly fine - but
>> the cgroup file ve.start_timespec - with your patch it should rather be
>> called ve.clock_monotonic.
> 
> Fine by me. Will update.
> 
>>> Vladimir, maybe I misunderstand you, could you please provide
>>> the pseudocode how you imagine it could work? I mean without
>>> in-kernel time normalization. I suspect I miss something obvious.
>>
>> Before suspending a container, you call clock_gettime for
>> CLOCK_MONOTONIC on the host, then read ve.start_timespec, then save the
>> difference to the image. On restore you read CLOCK_MONOTONIC on the
>> destination host and write (clock - difference) to ve.start_timepsec.
>> This would require more work from userspace though.
> 
> And that's the problem. Currently we simply read this members
> from cgroup via libvzctl script, and write them back on the
> restore via script as well (and save the values itself inside
> libvzctl specific files because I don't want to bring some
> non-generic functionality into CRIU). In future (hopefully
> not that long) we will implement that named 'custom cgroup
> properties' engine in CRIU and we simply pass the cgroup
> file names into CRIU options so c/r will be done
> automatically.

For now we can keep a patch in vz-criu spec file for that, can't we?

> If we have to do _additional_ computation inside CRIU
> I fear this gonna be a way less convenient. So personally
> I would prefer the current scheme instead.
> 
> 	Cyrill
> .
>