[Xen-devel] [PATCH] Add hypercall to mark superpages to improve performance

[Dave McCracken <dcm@xxxxxxxx>]

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

Attachment: xen-unstable-fhpage-1.patch
Description: Text Data

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