Messages in this thread | ![/](/images/icornerl.gif) | | Subject | RE: memory hotremove prototype, take 3 | Date | Wed, 3 Dec 2003 09:57:20 -0800 | From | "Luck, Tony" <> |
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> > IMHO, To hot-remove memory, memory attribute should be divided > > into Hotpluggable and no-Hotpluggable, and each attribute memory > > should be allocated each unit(ex. node). > > Why? I still don't get that -- we should be able to use the virtual > addressing mechanism of any CPU to swap under the rug any virtual > address without needing to do anything more than allocate a page frame > for the new physical location (I am ignoring here devices that are > directly accessing physical memory--a callback in the device > model could > be added to require them to reallocate their buffers). > > Or am I deadly and naively wrong?
Most (all?) Linux implementations make use of a large area of memory that is mapped 1:1 (with a constant offset) from kernel virtual space to physical space. Kernel memory is allocated in this virtual area. If the processor supports some form of large pages in the TLB, this 1:1 area uses the large pages ... so it would require some major surgery to remap portions of this area, and would have a negative effect on performance (since you'd take more TLB misses). It might even be a correctness issue if the structures in this area were needed to handle small page TLB faults in the area itself.
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