Messages in this thread | | | Subject | Re: [PATCH] zerocopy NFS updated | From | Andi Kleen <> | Date | 10 Apr 2002 21:32:22 +0200 |
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Hirokazu Takahashi <taka@valinux.co.jp> writes:
> But I wonder about sendpage. I guess HW IP checksum for outgoing > pages might be miscalculated as VFS can update them anytime. > New feature like COW pagecache should be added to VM and they > should be duplicated in this case.
For hw checksums it should not be a problem. NICs usually load the packet into their packet fifo and compute the checksum on the fly and then patch it into the header in the fifo before sending it out. A NIC that would do slow PCI bus mastering twice just to compute the checksum would be very dumb and I doubt they exist (if yes I bet it would be faster to do software checksumming on them). When the NIC only accesses the memory once there is no race window.
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