When transferring data from RAM to a network interface, pinning a page can be used, but suppose that system calls to pin and unpin pages each take 1 sec Copying takes 5 bytes nsec using DMA but 20 nsec per byte using programmed I O How big does a packet have to be before pinning the page and using ...

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When transferring data from RAM to a network interface, pinning a page can be used, but suppose

Question:

When transferring data from RAM to a network interface, pinning a page can be used, but suppose that system calls to pin and unpin pages each take 1 μ sec. Copying takes 5 bytes/nsec using DMA but 20 nsec per byte using programmed I/O. How big does a packet have to be before pinning the page and using DMA is worth it?