Video performance may decrease when a Windows Server 2008 or Windows Server 2008 R2 based computer has the Hyper-V role enabled and an accelerated display adapter installed

This issue occurs when a device driver or other kernel mode component makes frequent memory allocations by using the PAGE_WRITECOMBINE protection flag set while the hypervisor is running. When the kernel memory manager allocates memory by using the WRITECOMBINE attribute, the kernel memory manager must flush the Translation Lookaside Buffer (TLB) and the cache for the specific page. However, when the Hyper-V role is enabled, the TLB is virtualized by the hypervisor. Therefore, every TLB flush sends an intercept into the hypervisor. This intercept instructs the hypervisor to flush the virtual TLB. This is an expensive operation that introduces a fixed overhead cost to virtualization. Usually, this is an infrequent event in supported virtualization scenarios. However, some video graphics drivers may cause this operation to occur very frequently during certain operations. This significantly magnifies the overhead in the hypervisor.