Re: subobj-rmap

From: Martin J. Bligh (mbligh@aracnet.com)
Date: Sun Apr 06 2003 - 17:25:08 EST


>> We can always leave the sys_remap_file_pages stuff using pte_chains,
>
> not sure why you want still to have the vm to know about the
> mmap(VM_NONLINEAR) hack at all.
>
> that's a vm bypass. I can bet the people who wants to use it for running
> faster on the the 32bit archs will definitely prefer zero overhead and
> full hardware speed with only the pagetable and tlb flushing trash, and
> zero additional kernel internal overhead. that's just a vm bypass that
> could otherwise sit in kernel module, not a real kernel API.

Well, you don't get zero overhead whatever you do. You either pay the
cost at remap time of manipulating sub-objects, or the cost at page-touch
time of the pte_chains stuff. I suspect sub-objects are cheaper if we
read /write the 32K chunks, not if people mostly just touch one page
per remap though.

What do you think about using this for the linear stuff though?

M.

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