[Qemu-devel] Live migration broken when under heavy IO

[Anthony Liguori]

The basic issue is that:

migrate_fd_put_ready():    bdrv_flush_all();

Does:

block.c:

foreach block driver:
  drv->flush(bs);

Which in the case of raw, is just fsync(s->fd).

Any submitted request is not queued or flushed which will lead to the 
request being dropped after the live migration.

Is anyone working on fixing this?  Does anyone have a clever idea how to 
fix this without just waiting for all IO requests to complete?

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Regards,

Anthony Liguori