I am seeing EQ overruns in SDP stress tests: if the 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.
This is similiar to what we have with command interface:
/*
* cmd_event() may add more commands.
* The card will think the queue has overflowed if
* we don't tell it we've been processing events.
*/
However, for completion events, we *don't* want to update the consumer
index on each event. So, perform EQ doorbell coalescing: allocate EQs
with some spare EQEs, and update once we run out of them.
The value 0x80 was selected to avoid any performance impact.
Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
92898522e3