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[Xen-devel] Re: [PATCH 3/7] libxenlight resend: 8mb physmap slack for pv

To: Vincent Hanquez <vincent.hanquez@xxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH 3/7] libxenlight resend: 8mb physmap slack for pv domains
From: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
Date: Thu, 03 Dec 2009 11:03:58 -0500
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>
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No extra memory is being allocated at all in any way. The only impact is a wee bit larger p2m table.
Vincent Hanquez wrote:
On Wed, Dec 02, 2009 at 06:00:31PM +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.

Note that this does not allocate any extra memory
to the domain, it simply extends the physmap with
some extra room for "bounce bufffering back" pfn's
that are yielded to dom0.

but the memory is still going off from somewhere isn't it ?
all those random memory constants spread around in xend took us quite some time
to get things right in XCP and XenServer, and also for keeping the library as
dumb as possible, I'ld rather have the toolstack set the field in the structure
(even if it end up beeing 8M all the time) than starting adding those things.

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