[ofa-general] [PATCH] ipoib/cm: use common CQ for all TX QPs

[Pradeep Satyanarayana]

Michael S. Tsirkin wrote:
> Use common CQ for all TX QPs: keep a per-device counter of outstanding TX WRs,
> and stop the interface when this counter reaches the send queue size, to avoid
> CQ overruns.  This should help reduce the number of interrupts for
> bi-directional traffic (such as TCP).

CQ overrun generates asynchronous errors. If CQ overruns are avoided, how does that 
reduce interrupts?

On a side note, as a further extension to this idea, would it be worth considering 
sendq_size and recvq_size being device specific in the future, instead of being 
module specific?
> 
> This helps fix "driver is hogging interrupts" errors reported for IPoIB send side.
> See e.g. https://bugs.openfabrics.org/show_bug.cgi?id=508
> 
In bug 508, timer ticks were lost because some device was hogging interrupts. 
What is the association between dropping packets and hogging interrupts?
Can you expand on that?

Pradeep