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Message-ID: <4A36B025.2080602@us.ibm.com>
Date: Mon, 15 Jun 2009 15:33:41 -0500
From: Anthony Liguori <aliguori@us.ibm.com>
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Subject: [Qemu-devel] Live migration broken when under heavy IO
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To: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, kvm-devel <kvm@vger.kernel.org>

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?

---

Regards,

Anthony Liguori