From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dotan Barak Subject: Re: CQEs in unreliable connection Date: Thu, 28 Nov 2013 21:49:11 +0200 Message-ID: <52979E37.3080000@gmail.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Anuj Kalia Cc: "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-rdma@vger.kernel.org Hi Anuj. On 28/11/2013 14:24, Anuj Kalia wrote: > Hi. > > I had 2 questions related to RDMA operations (reads and writes) over > unreliable connections: > > 1. Are WQEs issued over an unreliable connection supposed to generate > CQEs? The Infiniband spec says that such WQEs may not generate an > 'ACK'. I'm confused if ACK refers to CQE. ACK is an acknowledgment that was sent over the wire that the message was received by the remote side. CQE is a mechanism to indicate that a Work Request isn't outstanding anymore. In RC QP, a CQE with successful status of a Send Request means that an ACK was received by the sender. However, In UC QP, a CQE with successful status of a Send Request means that the message was sent; it isn't indicate that the message was received by the remote side ... (You will get a successful CQE even if the remote side didn't receive this message) > > 2. If the status of the work completion (fetched using ibv_poll_cq()) > is IBV_WC_SUCCESS, does it mean that the operation was successful at > the remote host (even though we used an unreliable connection)? I answered your answer above ... If you want some more information, you are welcome to read it in: http://www.rdmamojo.com/2013/06/01/which-queue-pair-type-to-use/ Thanks Dotan -- 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