On Friday, October 10/09/20, 2020 at 01:47:04 +0300, Max Gurtovoy wrote: > > On 10/8/2020 9:59 PM, Krishnamraju Eraparaju wrote: > >On Thursday, October 10/08/20, 2020 at 13:12:39 +0000, Bernard Metzler wrote: > >>-----"Krishnamraju Eraparaju" <krishna2@xxxxxxxxxxx> wrote: ----- > >> > >>>To: "Max Gurtovoy" <mgurtovoy@xxxxxxxxxx> > >>>From: "Krishnamraju Eraparaju" <krishna2@xxxxxxxxxxx> > >>>Date: 10/07/2020 05:36AM > >>>Cc: "Sagi Grimberg" <sagi@xxxxxxxxxxx>, linux-rdma@xxxxxxxxxxxxxxx, > >>>"Potnuri Bharat Teja" <bharat@xxxxxxxxxxx>, "Max Gurtovoy" > >>><maxg@xxxxxxxxxxxx> > >>>Subject: [EXTERNAL] Re: reduce iSERT Max IO size > >>> > >>>On Sunday, October 10/04/20, 2020 at 00:45:26 +0300, Max Gurtovoy > >>>wrote: > >>>>On 10/3/2020 6:36 AM, Krishnamraju Eraparaju wrote: > >>>>>On Friday, October 10/02/20, 2020 at 13:29:30 -0700, Sagi Grimberg > >>>wrote: > >>>>>>>Hi Sagi & Max, > >>>>>>> > >>>>>>>Any update on this? > >>>>>>>Please change the max IO size to 1MiB(256 pages). > >>>>>>I think that the reason why this was changed to handle the worst > >>>case > >>>>>>was in case there are different capabilities on the initiator and > >>>the > >>>>>>target with respect to number of pages per MR. There is no > >>>handshake > >>>>>>that aligns expectations. > >>>>>But, the max pages per MR supported by most adapters is around 256 > >>>pages > >>>>>only. > >>>>>And I think only those iSER initiators, whose max pages per MR is > >>>4096, > >>>>>could send 16MiB sized IOs, am I correct? > >>>>If the initiator can send 16MiB, we must make sure the target is > >>>>capable to receive it. > >>>I think max IO size, at iSER initiator, depends on > >>>"max_fast_reg_page_list_len". > >>>currently, below are the supported "max_fast_reg_page_list_len" of > >>>various iwarp drivers: > >>> > >>>iw_cxgb4: 128 pages > >>>Softiwarp: 256 pages > >>>i40iw: 512 pages > >>>qedr: couldn't find. > >>> > >>For siw, this limit is not determined by resource constraints. > >>We could bump it up to 512, or higher. What is a reasonable > >>maximum, from iSER view? > >If the most common IO sizes are 4K & 8K, then the reasonable max IO size of > >256 pages(1 MiB) would be appropriate, by default. currently, NVMet-rdma > >also limits max IO size to 1MiB. > > We can set a default to 1MiB, and add module param that can increase > this size to a max IO size of 16MiB. > > I'll sent a patch early next week. Thanks Max! > > > >> > >>>For iwarp case, if 512 is the max pages supported by all iwarp > >>>drivers, > >>>then provisioning a gigantic MR pool at target(to accommodate never > >>>used > >>>16MiB IO) wouldn't be a overkill? > >>>>>>If we revert that it would restore the issue that you reported in > >>>the > >>>>>>first place: > >>>>>> > >>>>>>-- > >>>>>>IB/isert: allocate RW ctxs according to max IO size > >>>>>I don't see the reported issue after reducing the IO size to 256 > >>>>>pages(keeping all other changes of this patch intact). > >>>>>That is, "attr.cap.max_rdma_ctxs" is now getting filled properly > >>>with > >>>>>"rdma_rw_mr_factor()" related changes, I think. > >>>>> > >>>>>Before this change "attr.cap.max_rdma_ctxs" was hardcoded with > >>>>>128(ISCSI_DEF_XMIT_CMDS_MAX) pages, which is very low for single > >>>target > >>>>>and muli-luns case. > >>>>> > >>>>>So reverting only ISCSI_ISER_MAX_SG_TABLESIZE macro to 256 doesn't > >>>cause the > >>>>>reported issue. > >>>>> > >>>>>Thanks, > >>>>>Krishnam Raju. > >>>>>>Current iSER target code allocates MR pool budget based on queue > >>>size. > >>>>>>Since there is no handshake between iSER initiator and target on > >>>max IO > >>>>>>size, we'll set the iSER target to support upto 16MiB IO > >>>operations and > >>>>>>allocate the correct number of RDMA ctxs according to the factor > >>>of MR's > >>>>>>per IO operation. This would guaranty sufficient size of the MR > >>>pool for > >>>>>>the required IO queue depth and IO size. > >>>>>> > >>>>>>Reported-by: Krishnamraju Eraparaju <krishna2@xxxxxxxxxxx> > >>>>>>Tested-by: Krishnamraju Eraparaju <krishna2@xxxxxxxxxxx> > >>>>>>Signed-off-by: Max Gurtovoy <maxg@xxxxxxxxxxxx> > >>>>>>-- > >>>>>> > >>>>>>>Thanks, > >>>>>>>Krishnam Raju. > >>>>>>>On Wednesday, September 09/23/20, 2020 at 01:57:47 -0700, Sagi > >>>Grimberg wrote: > >>>>>>>>>Hi, > >>>>>>>>> > >>>>>>>>>Please reduce the Max IO size to 1MiB(256 pages), at iSER > >>>Target. > >>>>>>>>>The PBL memory consumption has increased significantly after > >>>increasing > >>>>>>>>>the Max IO size to 16MiB(with commit:317000b926b07c). > >>>>>>>>>Due to the large MR pool, the max no.of iSER connections(On > >>>one variant > >>>>>>>>>of Chelsio cards) came down to 9, before it was 250. > >>>>>>>>>NVMe-RDMA target also uses 1MiB max IO size. > >>>>>>>>Max, remind me what was the point to support 16M? Did this > >>>resolve > >>>>>>>>an issue?
