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Re: [Qemu-devel] Debugging Migration
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] Debugging Migration |
Date: |
Tue, 6 Oct 2015 20:00:13 +0100 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
* John Snow (address@hidden) 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 / address@hidden / Manchester, UK
- [Qemu-devel] Debugging Migration, John Snow, 2015/10/08
- Re: [Qemu-devel] Debugging Migration,
Dr. David Alan Gilbert <=
- Re: [Qemu-devel] Debugging Migration, Denis V. Lunev, 2015/10/08
- Re: [Qemu-devel] Debugging Migration, John Snow, 2015/10/08
- Re: [Qemu-devel] Debugging Migration, Denis V. Lunev, 2015/10/08
- [Qemu-devel] [RFC 0/8] QEMUFile-way to gather VM's memory statistics, Denis V. Lunev, 2015/10/08
- [Qemu-devel] [PATCH 3/8] migration: add new capability test-only, Denis V. Lunev, 2015/10/08
- Re: [Qemu-devel] [PATCH 3/8] migration: add new capability test-only, Eric Blake, 2015/10/08
- Re: [Qemu-devel] [PATCH 3/8] migration: add new capability test-only, Denis V. Lunev, 2015/10/09
- Re: [Qemu-devel] [PATCH 3/8] migration: add new capability test-only, Dr. David Alan Gilbert, 2015/10/09
- [Qemu-devel] [PATCH 7/8] migration: new migration test mode, Denis V. Lunev, 2015/10/08
- Re: [Qemu-devel] [PATCH 7/8] migration: new migration test mode, Dr. David Alan Gilbert, 2015/10/08