How a app can know that it had been dumping by criu

[FuwuerRyu]

How a app can know that it had been dumping by criu

[adrianreber]

Not really and that is the beauty of it.

You probably can detect migration by comparing MAC addresses and information from the system, but a checkpoint should not really be detectable.

Before the time namespace existed we have seen that database detect migration by reading clock monotonic and if it jumps it aborts. You could also read the local clock monotonic and if it jumps too much you could say it might be checkpointed, but I doubt that this works reliably.

If you want to signal your process that it was checkpointed you could send a signal using an action script.

I think it is really difficult to detect.

Maybe someone else has additional information.

[FuwuerRyu]

Not really and that is the beauty of it.

You probably can detect migration by comparing MAC addresses and information from the system, but a checkpoint should not really be detectable.

Before the time namespace existed we have seen that database detect migration by reading clock monotonic and if it jumps it aborts. You could also read the local clock monotonic and if it jumps too much you could say it might be checkpointed, but I doubt that this works reliably.

If you want to signal your process that it was checkpointed you could send a signal using an action script.

I think it is really difficult to detect.

Maybe someone else has additional information.

Could you let me know how criu stop the process before dumping it

[adrianreber]

Could you let me know how criu stop the process before dumping it

This is something which documented quite well. Either ptrace or cgroup freezer.

[adrianreber]

Why are you asking this question? If you would tell us what your goal is we could maybe help you better.

[FuwuerRyu]

Why are you asking this question? If you would tell us what your goal is we could maybe help you better.

Thank you very much. I am trying to migrate GPU APP with criu, so I need to dump GPU resource after criu freeze it and before criu dumpe it. If I can get the signal of freezing, I can store all GPU resources before dumping.

[adrianreber]

Why are you asking this question? If you would tell us what your goal is we could maybe help you better.

Thank you very much. I am trying to migrate GPU APP with criu, so I need to dump GPU resource after criu freeze it and before criu dumpe it. If I can get the signal of freezing, I can store all GPU resources before dumping.

Okay, if you control your application you can just use CRIU's action-scripts to send a signal (man 7 signal) for example. Once your applications receives your custom signal you can handle the GPU resources and once that is done CRIU can dump the non-GPU part of the process. Or you could create a file somewhere and if that file exists you can do something in you application. Or open a socket. If you control your application it should be easy to do.

[FuwuerRyu]

Got it. Good idea. Thank you very much again!