I encountered today a case, where default RX_RING_SIZE
was too small for the traffic going thru. (3c59x driver,
and NAT-router application.)
One related problem is, that the RING_SIZE is hard #define
parameter in most driver sources without ability to adjust
it during runtime. (e.g. "modprobe zzzz rx_ring_size=512")
Possibly even an ifconfig:able parameter, which works
also for statically compiled kernels. (But needs new
ifconfig machinery...)
The case at hand was solved by editing kernel sources, and
compiling a new kernel, but now I am looking for a more
generic approach.
Clearly pre-allocing 500 buffers of 1.6 kB in size does
eat a bit much of kernel memory which usual workstation
does not get benefit from, but server or router would get
benefits.
Having the rx_ring_size ifconfig tunable would help with
adjusting interface for reception, but adding ifconfig
parameters is ... not trivial.
Alternate might be sysctl tunability -- even as a global
'dev.eth.rx_ring_size' (or 'net.dev.eth.rx_ring_size')
which supplies (default) ring size for initialization of
the interface where such rings exist at all...
Possibly there should also be tx_ring_size, which need not
be same size as the rx_ring_size.
Unadjusted default value for both could be 16.
All in all, this needs near uniquitous changes in driver
init codes accross lots of network drivers.
Comments ? Suggestions ?
/Matti Aarnio
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