From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roland Dreier Subject: Re: How to know if SRQ is being used in SRP? Date: Thu, 05 Aug 2010 11:08:21 -0700 Message-ID: References: <201008031602.37294.bvanassche@acm.org> <4C59C34F.2000400@vlnb.net> <8BAAFD34FEF6492A8E3B43698E454B3D@md.baymicrosystems.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <8BAAFD34FEF6492A8E3B43698E454B3D-+IkoAhRkys/CbFgIbBqbbjGjJy/sRE9J@public.gmane.org> (Suresh Shelvapille's message of "Thu, 5 Aug 2010 12:38:55 -0400") Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Suresh Shelvapille Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org > I have the envious task of figuring out whether SRQ is being used in > an SRP application (which I have very little knowledge about). I > only have IB transport layer traces from the customer. From the > traces I can see Valid Credits in the Syndrome field of the AETH in > RDMA_ReadResponse_First/last messages. Although there are a bunch > of RC SENDs where the AETH syndrome field is Invalid, unfortunately > I cannot seem to correlate these RC SENDS with the RDMA > read/responses. My questions is, since the RDMA response AETH field > has valid CC credits is it saying SRQ is not being used? As I guess you know, if end-to-end credits are used on an RC connection, then SRQ cannot be used on that connection. The opposite implication does not hold: eg a TCA might not implement the optional end-to-end flow control protocol, and hence a non-SRQ connection might still not use end-to-end flow control. Also end-to-end flow control is negotiated for each direction of a connection independently, so you might see valid end-to-end credits sent in only one direction. Essentially the only thing you can learn from a wire-level trace is the following: if you see an AETH with valid end-to-end credits being sent from CA X, then the corresponding receive queue on CA X is not attached to an SRQ. I don't believe there is anything further you can deduce. (Certainly invalid end-to-end credits do not imply that an SRQ is being used, they simply imply that the end-to-end flow control protocol is not in use) - R. -- Roland Dreier || For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/index.html -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html