Xen devel - Mar 2008 - why each process needs a separate page for kernel''s pgd table in PV x86_64?

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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