North American Network Operators Group
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Re: Software router state of the art

  • From: Petri Helenius
  • Date: Sat Jul 26 13:41:16 2008
William Herrin wrote:
"ethtool -c". Thanks Sargun for putting me on to "I/O Coalescing."

But cards like the Intel Pro/1000 have 64k of memory for buffering
packets, both in and out. Few have very much more than 64k. 64k means
32k to tx and 32k to rx. Means you darn well better generate an
interrupt when you get near 16k so that you don't fill the buffer
before the 16k you generated the interrupt for has been cleared. Means
you're generating an interrupt at least for every 10 or so 1500 byte
packets.
This is not true in the bus master dma mode how the cards are usually used. The mentioned memory is used only as temporary storage until the card can DMA the data into the buffers in main memory. Most Pro/1000 cards have buffering capability up to 4096 frames.

Pete