[CRIU] [PATCH] stats/pid-reuse: put stats to image directory instead of cwd

[Pavel Emelyanov]

On 03/26/2018 02:02 PM, Cyrill Gorcunov wrote:
> On Mon, Mar 26, 2018 at 01:43:11PM +0300, Pavel Emelyanov wrote:
>> On 03/26/2018 12:16 PM, Pavel Tikhomirov wrote:
>>> On 03/26/2018 11:54 AM, Pavel Emelyanov wrote:
>>>> On 03/26/2018 11:12 AM, Pavel Tikhomirov wrote:
>>>>> Statistics for a special dump/pre-dump/restore action should be
>>>>> collected in the images directory of these action. We need these for
>>>>> pid-reuse detection as we need to read the stats of parent predump.
>>>>
>>>> What's wrong with checking pid-reuse form stats sitting in workdir?
>>>
>>> We can read previous dump statistics from workdir before 
>>> cr_*dump_finish, I agree with that, it is easy.
>>>
>>> But Kirill says that "writing image outside of image directory is 
>>
>> Stats file is not an image. We just use PB format for it and reuse existing
>> image-writing machinery.
> 
> Stats file is context dependant and logically bound to images. At least
> keeping it inside image drectory gives you confidence the data written
> there belongs exactly to the images produced.

So are logs, but we keep them in workdir anyway.

> Because pid reuse uses
> data from stats to operate on memory engine it become not longer
> a random stat just to view, but mandatory data required for proper
> restore.

I've missed that fast somehow. What's there in stats image the pid-reuse needs?

> If you still prefer stats file to be on its own then I think we
> need use some other image to carry this information.
> 
>>> architectural problem", actually I think these way too for at least two 
>>> reasons:
>>>
>>> 1) When stats image is in images dir we can latter analize stats for 
>>> each iteration if we want it. Now doing migration in VZ7 we have only 
>>> stats of last dump in the end.
>>
>> The same problem's for log files (I hope nobody has moved them into images dir
>> so far), isn't it? Use separate workdir for each iteration.
> 
> Exactly, same problem. And for vz7 the logs are kept in the image
> directory via vzctl option passed. 

Gents, by default criu keeps work dir and images together, some efforts should be
done to keep them separately. What option are you talking about?

> Thus when a user comes to us with
> a problem we ask him to provide us logs from the image directory and
> if logs on self are not enough we can ask to pack images directory
> where the *complete* state of everything is present which we need
> to analyze a problem.
> .
>