Re: subobj-rmap

[Martin J. Bligh]

>> 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.