[CRIU] zdtm: lazy pages arguments

[Radostin Stoyanov]

On 14/09/18 08:46, Mike Rapoport wrote:
> Hi,
>
> On Thu, Sep 13, 2018 at 04:30:39PM +0100, Radostin Stoyanov wrote:
>> Hi all,
>>
>> I am trying to understand what is the difference between --lazy-pages,
>> --lazy-migrate and --remote-lazy-pages arguments of zdtm.
> --lazy-pages tests lazy restore from images. In this case dump works
> "normally", restore skips the memory pages that can be handled on demand
> and lazy-pages daemon handles the page faults and reads the memory contents
> from the image files.
>
> --remote-lazy-pages simulates post-copy memory migration. Here again, the
> dump works "normally", but the lazy-pages daemon does not read data from
> the image files but requests it "over the network" for the page-server. It
> is the page-server that reads memory pages from the images and simulates
> what 'dump --lazy-pages' wound have done.
>
> --lazy-migrate actually does post-copy migration. It cannot run with the
> host flavor because during post-copy migration the migrated tasks should
> exist both on the source and the destination.
Thank you Mike!

I added this description to the wiki page for future reference.
https://criu.org/ZDTM_test_suite#All_zdtm_tests

Radostin
>> Is it possible to combine them?
> Well, they do overlap, but there are code paths that are tested only in one
> of them.
> Nothing comes to mind right now, but I remember that there were bugs that
> showed up in one of the cases and didn't appear in others.
>
>
>
>> --lazy-pages was introduced with
>> https://github.com/checkpoint-restore/criu/commit/f59b45f
>>
>>     zdtm: check lazy-pages
>>
>>
>> --lazy-migrate was introduced with
>> https://github.com/checkpoint-restore/criu/commit/d499aea
>>
>>      zdtm: enable lazy migration testing
>>
>>
>> The --lazy-migrate option allows testing of lazy migration when running ns
>> or uns flavor.
>>
>> --remote-lazy-pages was introduced with
>> https://github.com/checkpoint-restore/criu/commit/c89a22a
>>
>>      zdtm: simulate lazy migration with page server that can send pages
>>
>>     Lazy migration requires both dumped and restored processes to coexist at
>>     the same time. This breaks some basic assumptions in the zdtm design.
>>     Simulation of lazy migration with the page server allows testing most of
>>     the involved code paths without major intervention into zdtm
>>     infrastructure.
>>
>>
>> Thanks,
>> Radostin
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