Re: TCP Checksum offload in 2.4.19

From: David S. Miller (davem@redhat.com)
Date: Fri Sep 06 2002 - 18:16:36 EST


   From: Bernd Eckenfels <ecki-news2002-09@lina.inka.de>
   Date: Sat, 7 Sep 2002 00:58:25 +0200
   
   thats why it makes sence to have zerocopy with hw-checksum. there is only a
   marginal time needed for a copy+chksum, but it is totally wasted time on
   zero copy environment.

You don't understand. Because it is too complicated to zerocopy
arbitrary anonymous user pages, we have to copy it into a stable
kernel buffer. Because we have to copy, we checksum at the
same time.

If you want zerocopy for user created data, create a file for
the process, mmap() it, write your contents, then sendfile()
the thing to the socket. End of story.

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