TCP/IP mbuf element size
Charles Steaderman
charlies at poliac.com
Thu Feb 13 00:53:16 UTC 2003
Hi all. I am working on an ethernet driver on an ARM CPU. When I am
requested to transmit data out of the ethernet port, I am given a chain
of mbufs. The chain is often times made up of many small buffers. For
example, when replying to a 1500 byte ping request, I receive 2 mbuf
chains. The first chain contains 3 elements of 14, 80, and 1420 bytes
respectfully. The second chain contains 3 elements of 34, 20, and 8
bytes respectfully. Unfortunately, the DMA controller on our chip does
not deal well with small buffers, and causes underflow errors in our
ethernet controller. Is there a way to tell the TCP/IP stack to give me
fewer, but larger, mbufs? I really don't want to have to copy the data
from the mbufs into a buffer prior to initiating a transfer.
Thanks,
- Charlie
--
Charlie Steaderman
charlies at poliac.com
VP Engineering
Poliac Research Corporation
Phone: 952.707.6245
Cel: 612.242.6364
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