[openib-general] [PATCH] mthca: eq doorbell coalescing + prevent even queque overrun

[Or Gerlitz]

Michael, Roland

Michael S. Tsirkin wrote:
> I am seeing EQ overruns in SDP stress tests: if CQ completion
> handler arms a CQ, this could generate more EQEs, so that
> EQ will never get empty and consumer index will never get updated.

There's something re CQ arming which i'd like to bring up.

I see that the mad, ipoib and srp CQ handlers work as follows: first - 
arm the CQ, second - poll the CQ in a loop till it is emtpy. What is the 
reasoning behind this approach? does it means that completions occurring 
while the handler is running cause interrupts which could be saved? is 
there any problem with first empty-ing the CQ and only then arming it?

The latter approach is taken by iser code. As far as i understand it can 
not cause the ib consumer to miss interrupts, am i wrong?

Or.