-----"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? >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? >
