* John Snow (js...@redhat.com) wrote:
> Is there a convenient way of "pausing" or stalling a live migration to
> allow methodical testing of race conditions?
>
> I'd like to instrument something along the lines of:
>
> (1) Live migration begins.
> (2) migration is artificially halted or paused, but QEMU is allowed to run.
> (3) Some additional qtest/QMP commands are received and processed.
> (4) migration is allowed to resume.
>
> Does anyone have perhaps even test patches to instrument this sort of
> thing, or is it up to detective john to add it if he wants it?
If you catch it during the iterative stage you can probably just
gdb or ctrl-z the destination and the migration thread should block;
or alternatively migrate to a pipe and similarly ctrl-z what ever is
there.
Mostly I do a few things:
1) use tracing to follow it
mostly just stderr tracing, but I've done systemtap scripts
for some hairy stuff.
2) Set the migration speed (migrate_set_speed) very very low
3) Keep the source busy dirtying memory.
Of course that does lead to the question of what fun problem are
you trying to debug?
Dave
> --js
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
