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Re: [Xen-devel] Will Xen 4.0 release use the pv-ops kernel despite it's

To: Tom Rotenberg <tom.rotenberg@xxxxxxxxx>
Subject: Re: [Xen-devel] Will Xen 4.0 release use the pv-ops kernel despite it's performance hit
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Mon, 21 Dec 2009 07:01:54 +0000
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Thread-topic: [Xen-devel] Will Xen 4.0 release use the pv-ops kernel despite it's performance hit
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It's the other way round: using newer pv_ops dom0 will require a newer
version of Xen (4.0, or perhaps a newer 3.4.x if I backport the patches).
Compatibility is not broken the other way round (new Xen, old dom0), and
never should be.

 -- Keir

On 21/12/2009 06:16, "Tom Rotenberg" <tom.rotenberg@xxxxxxxxx> wrote:

> OK.
> I just thought i saw Jeremy's mail about changing the APIC logic in
> Xen to conform to the pv-ops kernel, which i thought will cause new
> Xen not to work with old dom0 kernel. This isn't the case?
> On Sun, Dec 20, 2009 at 11:53 PM, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
> wrote:
>> On 20/12/2009 17:41, "Tom Rotenberg" <tom.rotenberg@xxxxxxxxx> wrote:
>>> Will Xen 4.0 release use the pv-ops kernel, despite the fact that it
>>> has about ~15% hit in performance?
>>> This is a major performance hit, and releasing a new Xen version with
>>> a 15% performance hit in the dom0 kernel compared to a previous
>>> version, will just cause people not to upgrade to Xen 4.0 (especially
>>> if Xen 4.0, won't support the old 2.6.18 xen kernel anymore).
>>> Is this performance issue going to be addressed prior to Xen 4.0 release?
>> Work on both stabilisation and performance will be ongoing. But bear in mind
>> that upgrading to Xen 4.0 will not require users to switch to pv_ops dom0.
>>  -- Keir

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