i have written a low latency coreaudio driver which sends and receives UDP packets containing audio out over the network interface to a special purpose piece of hardware i've built. In order to get the performance/latency/etc i needed when the machine was running under a heavy load (doing real time processing of live audio, etc) I had to modify the AppleGMACEthernet.kext driver so that the main loop in my coreaudio driver (get packet, copy buffers, call taketimestamp, send a packet out) gets called at primary interrupt time (highest priority in the system) by using checkForInterrupt instead of just interruptOccurred and having it call my coreaudio driver. I basically bypassed the whole networking stack. You might need to do something of that sort... -rimas --- Mike Smith <drivers@mu.org> wrote:
On Jan 15, 2004, at 1:31 AM, Stefan Werner wrote:
Are there other tweaks to enhance the latency of
networking? I don't
mind a decrease in throughput, I'm in one of the
rare cases where
bandwidth is not the limit. There are these
popular "bandwidth tuner"
tweaks where people change the system's TCP buffer
size with sysctls,
would shrinking the buffers give me any latency
improvements or will
that result in dropped packets?
It won't help; the system already tries to give you
the lowest possible
latency. There's not really any more blood to
squeeze from the stone.
It's important, back in the design stage, to take
into consideration
that you're going to be running in a multiprogrammed
environment and
try to take this into account there, rather than
trying to tweak a
system that can't give you guarantees to fit a
design that assumes a
particular value of "reasonable".
Obviously this isn't always possible.
= Mike
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