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Re: [Xen-devel] [RFC][PATCH 12/13] Kemari: use signal to save qemu state

To: Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [RFC][PATCH 12/13] Kemari: use signal to save qemu state for Kemari
From: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Date: Mon, 16 Mar 2009 18:05:20 +0000
Cc: "ospk-vm@xxxxxxxxxxxxx" <ospk-vm@xxxxxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Yoshiaki Tamura <tamura.yoshiaki@xxxxxxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>
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Stefano Stabellini writes ("Re: [Xen-devel] [RFC][PATCH 12/13] Kemari: use 
signal to save qemu state for Kemari"):
> Yoshiaki Tamura wrote:
> > This patch implements signal handler for saving QEMU status
> > quickly.  It also includes a feature borrowed from KVM-17, which
> > saves QEMU status quickly without repositioning file offset by
> > fseek.
> 
> We got rid of the signal interface not so long ago because it doesn't
> work for stubdoms.
> 
> The new way of asking qemu to save the VM state is writing a command on
> xenstore (look at xenstore.c:xenstore_process_dm_command_event).
> Would that work for you?

I think that in this case a signal-based interface is probably fine,
because it does indeed need very good performance which is difficult
to do with xenstore.

Ian.

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