[Xen-devel] why each process needs a separate page for kernel's

To:	xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject:	[Xen-devel] why each process needs a separate page for kernel's pgd table in PV x86_64?
From:	weiming <zephyr.zhao@xxxxxxxxx>
Date:	Mon, 24 Mar 2008 00:07:39 -0400
Delivery-date:	Sun, 23 Mar 2008 21:08:04 -0700
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Hi,

I notice that in the paravirtualized linux for x86_64, each process allocates 2 pages for mm->pgd: one for kernel's page table, the other for user's page table.

Why not let all processes share the kernel's page table? i.e., add a field in mm struct (like mm->kernel_pgd, ) and let it point to a page, which will be referenced by all process. This can save some 4K for each process forked.

Please correct me if I'm wrong.

Thanks,
Weiming

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[Xen-devel] why each process needs a separate page for kernel's pgd tabl