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RE: [Xen-ia64-devel]PATCH] Remove duplicate check is_running_on_xen

To: "Xu, Anthony" <anthony.xu@xxxxxxxxx>
Subject: RE: [Xen-ia64-devel]PATCH] Remove duplicate check is_running_on_xen
From: Alex Williamson <alex.williamson@xxxxxx>
Date: Tue, 16 Jan 2007 20:10:12 -0700
Cc: xen-ia64-devel <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
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On Wed, 2007-01-17 at 10:17 +0800, Xu, Anthony wrote:

> There are two duplicate checks as below, so there are two way to eliminate 
> one check.
> 1. eliminate check in xen_get_tpr, then xen_get_tpr will never be called on 
> bare metal,
>      but it's a little perfomance impact, due to there is another switch 
> inside __ia64_getreg.
> 2. eliminate check in xen_ia64_getreg, then xen_get_tpr will be called both 
> on para platform
>    or bare metal, it can produce better performance than option 1. so I 
> prefer this.

   Is the performance difference actually measurable?  I suspect it's
effectively within the noise of any benchmark.  I prefer option 1
because the leaf function when running on bare metal is the same as the
native kernel, so we're not duplicating code.  Thanks,

Alex Williamson                             HP Open Source & Linux Org.

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