On Wed, 7 Feb 2001 kuznet@xxxxxxxxxxxxx wrote:
> In any case, maximal latency is 5-7usec, which is not a big number
> for TCP with jumbo mtu, where latency is dominated by bulk dma.
> But, if my arithmetics is correct, this really puts theoretical
> limit on transmission of 1500 byte frames: ~90MB/sec.
> (BTW, Jes, you enabled tx host ring in the latest driver.
> Did you notice that it increases latency by ~1 usec?)
How many fragments are there in the typical tx packet? Are these machines
with 64 bit / 66 MHz PCI, or just plain old 32 bit 33 MHz? If it's a 33
MHz bus, the overhead for starting new PCI cycles to gather fragments
could be maxing out the bandwidth. A PCI analyzer could be helpful =)
-ben
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