PATCH: 2.2 series FEC driver performance improvements

Graham Stoney greyham at
Mon Aug 21 18:51:10 EST 2000

Hi gang,

I've been profiling TCP performance over the FEC, and have come up with a
patch which improves onchip FEC receive performance on the MPC855/860T
processors, by DMAing received data for large packets directly in a kernel
socket buffer instead of using eth_copy_and_sum to copy the packets.  There
is also a small improvement from leaving the packet buffer cached and
explicitly invalidating it, instead of making it uncached.  The net effect is
around 15% - 20% speedup in raw TCP throughput on a 50 MHz 855T.

Also included are the following minor fixes/speedups:
- Correctly transmitted packets are no longer counted as having errors.

- Received packets that get dropped are no longer included in rx_packets.
  (as per drivers/net/skeleton.c).

- Receive FIFO overrun errors are now counted as such, rather than as CRC

- Avoid reading buffer descriptor status bits multiple times, especially since
  the descriptors themselves are still uncached.

Please let me know what you think!

The patch is available at:

Graham Stoney
Principal Hardware/Software Engineer
Canon Information Systems Research Australia
Ph: +61 2 9805 2909  Fax: +61 2 9805 2929

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