Hi Mandeep,
Mandeep Singh Baines wrote:
Hi James,
I like the idea of staying in poll longer.
My comments are similar to what Jamal and Stephen have already said.
A tunable (via sysfs) would be nice.
A timer might be preferred to jiffy polling. Jiffy polling will not increase
latency the way a timer would. However, jiffy polling will consume a lot more
CPU than a timer would. Hence more power. For jiffy polling, you could have
thousands of calls to poll for a single packet received. While in a timer
approach the numbers of polls per packet is upper bound to 2.
Why would using a timer to hold off the napi_complete() rather than
jiffy count limit the polls per packet to 2?
I think it may difficult to make poll efficient for the no packet case because,
at a minimum, you have to poll the device state via the has_work method.
Why wouldn't it be efficient? It would usually be done by reading an
"interrupt pending" register.
If you go to a timer implementation then having a tunable will be important.
Different appications will have different requirements on delay and jitter.
Some applications may want to trade delay/jitter for less CPU/power
consumption and some may not.
I agree. I'm leaning towards a new ethtool parameter to control this to
be consistent with other per-device tunables.
imho, the work should definately be pursued further:)
Thanks Mandeep. I'll try. :)
--
James Chapman
Katalix Systems Ltd
http://www.katalix.com
Catalysts for your Embedded Linux software development
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