[ewg] Re: [ofa-general] [PATCH] IB/ipoib: fix net queue lockup

Roland Dreier rdreier at cisco.com
Wed Apr 30 20:05:43 PDT 2008


 > we haves seen a few other cases where a large tx queue is needed. I
 > think we should choose a larger default value than the current 64.

maybe yes, maybe no... what are the cases where it is needed?

The send queue is basically acting as a "shock absorber" for bursty
traffic.  If the queue is filling up because of a steady traffic rate,
then making the queue bigger means it will just take a little longer to
fill.  The way a longer send queue helps I guess is if the send queue is
emptying out before the transmit queue is woken up...

with small packets I suppose it doesn't take long for the send queue to
drain completely.

 - R.




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