From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Steve Wise" Subject: RE: [PATCH rdma-next 0/3] Support out of order data placement Date: Mon, 12 Jun 2017 15:57:29 -0500 Message-ID: <085201d2e3be$81070ce0$831526a0$@opengridcomputing.com> References: <20170612064918.12510-1-leon@kernel.org> <074a01d2e39f$edc28860$c9479920$@opengridcomputing.com> <3fa7a4b5-5c19-8c6a-d78b-93219a9be888@intel.com> <1828884A29C6694DAF28B7E6B8A82373AB142A9B@ORSMSX109.amr.corp.intel.com> <1828884A29C6694DAF28B7E6B8A82373AB142BEC@ORSMSX109.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Return-path: In-Reply-To: <1828884A29C6694DAF28B7E6B8A82373AB142BEC-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org> Content-Language: en-us Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "'Hefty, Sean'" , "'Dalessandro, Dennis'" , 'Parav Pandit' , 'Leon Romanovsky' , 'Doug Ledford' Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, 'Idan Burstein' List-Id: linux-rdma@vger.kernel.org > > > When transmitter and receiver is enabled to do so, as I described in > > overview section of Documentation, it helps > > > (a) to avoid retransmission - improves network utilization > > > (b) reduces latency due to timers not kicking in. > > > > Yes those benefits are clear. I see no reason why it shouldn't always > > be > > done is my point. Application shouldn't have to care and there is no > > need to make this an additional flag. > > The app cares when data from write 2 can be written at the target before data > from write 1, especially if the writes target the same memory buffers. (At least I > think this is the intent of exposing this to the app.) > > Note that the provider can always provide stronger ordering than what the app > needs. My understanding is that IB or IW apps should never assume ingress write or read response data is _placed_ into local memory in the order it was transmitted from the peer. The only guarantee is that the _indication_ of the arrived data preserve the sender's ordering. However, I'm thinking that there are applications out there that spin polling local memory that is the target of a write or read response and assume the last bit of that memory will get written last... -- 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