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. > > > >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? > > >
