Re: [Xen-devel] [PATCH] iommu/quirk: disable shared EPT for Sandybridge and earlier processors.

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 28/08/15 16:41, "Anshul Makkar anshul.makkar"@citrix.com wrote:
> From: anshulma <anshul.makkar@xxxxxxxxxx>
>
> Sandybridge or earlier processors don't have huge page support for
> IOTLB which leads to fallback on 4k pages and causes performance issues.
>
> Shared EPT will be disabled only if the user has not provided explicit
> choice on the command line.
>
> Signed-off-by: Anshul Makkar <anshul.makkar@xxxxxxxxxx>

As a note concerning the performance issues, for some IO workloads, this
nets a 40% throughput improvement.

We did not observe any IO workloads which had a worse performance as a
result of disabling shared ept.

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

~Andrew

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