RE: [PATCH 3/5] IB/isert: Limit the number of SG elements per work request

["Steve Wise" <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>]

> On 06/28/2016 04:33 PM, Steve Wise wrote:
> >> -----Original Message-----
> >> From: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org [mailto:linux-rdma-
> >> owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org] On Behalf Of Bart Van Assche
> >> Sent: Tuesday, June 28, 2016 6:27 AM
> >> To: Doug Ledford
> >> Cc: Christoph Hellwig; Sagi Grimberg; Nicholas A. Bellinger; Parav Pandit;
> Laurence
> >> Oberman; linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> >> Subject: [PATCH 3/5] IB/isert: Limit the number of SG elements per work request
> >>
> >> Limit the number of SG elements per work request to what the queue
> >> pair supports.
> >>
> >
> > Hey Bart, do you think this patch fixes this error we're seeing?
> >
> > isert: isert_rdma_rw_ctx_post: Cmd: ffff880f30eb0278 failed to post RDMA res
> 
> Hello Steve,
> 
> Do you perhaps know how many SGE elements the failed work request
> contains? The reason I came up with the max_sge patch is because I
> noticed that the ib_srpt driver reported ib_post_send() failures for
> certain RDMA work requests. A debug printk() confirmed that
> ib_post_send() failed because the following test in the mlx4 driver was hit:
> 
> 		if (unlikely(wr->num_sge > qp->sq.max_gs)) {
> 			err = -EINVAL;
> 			*bad_wr = wr;
> 			goto out;
> 		}
> 
> For the mlx4 HCA in my test setup max_sge == 32, max_sge_rd == 30 and
> with the QP creation parameters I used max_gs == 28.
> 
> Bart.
> 

I'll let you know as I gather more data.  For now I'm retrying with patches 1-3 of this series to see if it alleviates the problem.  

Stevo

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