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[Xen-devel] [PATCH] Add hypercall to mark superpages to improve performa
| To: | Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
|---|---|
| Subject: | [Xen-devel] [PATCH] Add hypercall to mark superpages to improve performance |
| From: | Dave McCracken <dcm@xxxxxxxx> |
| Date: | Wed, 28 Apr 2010 09:33:20 -0500 |
| Cc: | Xen Developers List <xen-devel@xxxxxxxxxxxxxxxxxxx> |
| Delivery-date: | Wed, 28 Apr 2010 07:34:29 -0700 |
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The current method of mapping hugepages/superpages in the hypervisor involves updating the reference counts of every page in the superpage. This has proved to be a significant performance bottleneck. This patch adds a pair of MMUEXT hypercalls to mark and unmark a superpage. Once the superpage is marked, the type is locked to writable page until a companion unmark is done. When that superpage is subsequently mapped, only the first page needs to be reference counted. There are checks when the superpage is marked and unmarked to make sure no individual page mappings have skewed the reference counts. Dave McCracken Oracle Corp
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