On Mon, 2017-06-12 at 16:19 +0000, Parav Pandit wrote: > Hi Bart, > > > -----Original Message----- > > From: linux-rdma-owner@xxxxxxxxxxxxxxx [mailto:linux-rdma- > > owner@xxxxxxxxxxxxxxx] On Behalf Of Bart Van Assche > > Sent: Monday, June 12, 2017 10:28 AM > > To: leon@xxxxxxxxxx; dledford@xxxxxxxxxx > > Cc: linux-rdma@xxxxxxxxxxxxxxx; Idan Burstein <idanb@xxxxxxxxxxxx> > > Subject: Re: [PATCH rdma-next 0/3] Support out of order data placement > > > > On Mon, 2017-06-12 at 09:49 +0300, Leon Romanovsky wrote: > > > Out of order data placement capability indicates that if HCA receives > > > out of order RDMA packets, their data placement can be done at the > > > desired memory destination given in the packet(s). This is applicable > > > to RDMA read and write operations. > > > > Hello Leon and Parav, > > > > Since PCIe writes can be executed out of order, shouldn't that be mentioned > > in Documentation/infiniband/out_of_order.txt? See also the > > documentation of the Device Control Register and the Enable Relaxed > > Ordering bit in the PCIe spec. > > There is no change in the way PCIe writes are done with respect to this per QP > bit. Meaning, if this bit is cleared, PCIe subsystem can still do out of order > writes depending on relaxed ordering flag. Hello Parav, That's why I asked to mention PCIe write reordering in out_of_order.txt. Someone who is reading that document could be mislead to assume that if the HCA does not reorder writes that no reordering will occur. > > Additionally, since not handling out-of-order RDMA writes correctly is an > > ULP bug and since there are more ULPs that handle out-of-order writes > > correctly than ULPs that don't handle out-of-order writes correctly, if a new > > flag is introduced, shouldn't that be a flag to disable out-of-order writes? > > Not sure I understood correctly. This bit is not a bug fix for ULPs who don't > handle out-of-order writes. As I described in Documentation, "Out of order data > placement capability indicates that if HCA receives out of order RDMA packets, > their data placement can be done at the desired memory destination given in the > packet(s). This is applicable to RDMA read and write operations." This flag > indicates that - in above condition, HCA can do data placement out-of-order. > Without enabling this flag, when HCA receives out of order packets, it would drop > them due to PSN sequence error. > > So, - to your question - shouldn't that be a flag to disable out-of-order writes? > By default, its disabled at RDMA level. I don't think that your last two paragraphs mention anything that had not yet been mentioned in the four e-mails constituting your patch series. Additionally, I think my question was clear and unambiguous. So please reread my question. Thanks, Bart. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
