> From: Nicholas A. Bellinger [mailto:nab@xxxxxxxxxxxxxxx] > Sent: Wednesday, January 24, 2018 9:56 AM > > Hi Michal & Co, > > On Fri, 2018-01-19 at 19:33 +0000, Kalderon, Michal wrote: > > ________________________________________ > > From: Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx> > > Sent: Thursday, January 18, 2018 11:58 AM > > > > > Hi Shiraz, Michal & Co, > > Hi Nicholas, > > > > > Thanks for the feedback. Comments below. > > > > > A couple of thoughts. > > > > > First, would it be helpful to limit maximum payload size per I/O for > > > consumers based on number of iser-target sq hw sges..? > > > > I don't think you need to limit the maximum payload, but instead > > initialize the max_wr to be based on the number of supported SGEs > > Instead of what is there today: > > #define ISERT_QP_MAX_REQ_DTOS (ISCSI_DEF_XMIT_CMDS_MAX + \ > > ISERT_MAX_TX_MISC_PDUS + \ > > ISERT_MAX_RX_MISC_PDUS) Add the > > maximum number of WQEs per command, The calculation of number of > WQEs > > per command needs to be something like > > "MAX_TRANSFER_SIZE/(numSges*PAGE_SIZE)". > > > > Makes sense, MAX_TRANSFER_SIZE would be defined globally by iser-target, > right..? Globally or perhaps configurable by sysfs configuration? > > Btw, I'm not sure how this effects usage of ISER_MAX_TX_CQ_LEN + > ISER_MAX_CQ_LEN, which currently depend on > ISERT_QP_MAX_REQ_DTOS.. I think it can remain dependent on MAX_REQ_DTOS. > > Sagi, what are your thoughts wrt changing attr.cap.max_send_wr at runtime > vs. exposing a smaller max_data_sg_nents=32 for ib_devices with limited > attr.cap.max_send_sge..? For our device defining max_data_sg_nents didn't help on some scenarios, It seems that Frequency of the issue occurring increases with number of luns we Try to run over. > > > For some devices like ours, breaking the IO into multiple WRs > > according to supported number of SGEs doesn't necessarily means > performance penalty. > > > > AFAICT ading max_data_sg_nents for iser-target is safe enough work-around > to include for stable, assuming we agree on what the max_send_sg cut-off is > for setting max_data_sg_nents=32 usage from a larger default. I don't have > a string preference either way, as long as it can be picked up for 4.x stable. > > Sagi, WDYT..? ��.n��������+%������w��{.n����j� ����{ay� ʇڙ���f���h������_�(�階�ݢj"��������G����?���&��
