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Re: [Xen-devel] [PATCH 03/14]: libxenlight, 8MB slack for PV domains

To: Vincent Hanquez <vincent.hanquez@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 03/14]: libxenlight, 8MB slack for PV domains
From: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
Date: Tue, 01 Dec 2009 09:15:19 -0500
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>
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The 8mb slack is not real memory allocated. It's extra room in the pfn space. The memory's domain allocation remains capped at the amount intended. I haven't seen anyone in xen-devel for five years needing more slack than that ') Particularly since the network rx flipping path stopped being the default
Vincent Hanquez wrote:
On Mon, Nov 30, 2009 at 07:10:58PM +0000, Andres Lagar-Cavilla wrote:
Contemplate 8MB of slack for PV domains, since they
do ballooning (or flipping network rx) and need
some extra room in their pfn space.

Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>

this probably should be in the build structure. not magically adding 8 mb 
without the
toolstack knowing, otherwise no toolstack can provide more or less slacks on a
per domain basis. And it make precise memory handling a nightmare, and thus
dynamic memory handling too. in some way this parameter is just like the
shadow_memory one in the hvm build structure.

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