Hi Yi,

Finally found below patch [1] that fixed this issue.
With [1], I can see the speed of reset_controller operation[2] is obviously slow than before.


[1]
commit b7363e67b23e04c23c2a99437feefac7292a88bc
Author: Sagi Grimberg [off-list ref]
Date:   Wed Mar 8 22:03:17 2017 +0200

     IB/device: Convert ib-comp-wq to be CPU-bound

This is very unlikely.

I think that what made this go away is:

commit 777dc82395de6e04b3a5fedcf153eb99bf5f1241
Author: Sagi Grimberg [off-list ref]
Date:   Tue Mar 21 16:29:49 2017 +0200

     nvmet-rdma: occasionally flush ongoing controller teardown

     If we are attacked with establishments/teradowns we need to
     make sure we do not consume too much system memory. Thus
     let ongoing controller teardowns complete before accepting
     new controller establishments.


Cheers,
Sagi.
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