Hi Shiraz, Michal & Co, Thanks for the feedback. Comments below. On Mon, 2018-01-15 at 09:22 -0600, Shiraz Saleem wrote: > On Mon, Jan 15, 2018 at 03:12:36AM -0700, Kalderon, Michal wrote: > > > From: linux-rdma-owner@xxxxxxxxxxxxxxx [mailto:linux-rdma- > > > owner@xxxxxxxxxxxxxxx] On Behalf Of Nicholas A. Bellinger > > > Sent: Monday, January 15, 2018 6:57 AM > > > To: Shiraz Saleem <shiraz.saleem@xxxxxxxxx> > > > Cc: Amrani, Ram <Ram.Amrani@xxxxxxxxxx>; Sagi Grimberg > > > <sagi@xxxxxxxxxxx>; linux-rdma@xxxxxxxxxxxxxxx; Elior, Ariel > > > <Ariel.Elior@xxxxxxxxxx>; target-devel <target-devel@xxxxxxxxxxxxxxx>; > > > Potnuri Bharat Teja <bharat@xxxxxxxxxxx> > > > Subject: Re: SQ overflow seen running isert traffic with high block sizes > > > > > > Hi Shiraz, Ram, Ariel, & Potnuri, > > > > > > Following up on this old thread, as it relates to Potnuri's recent fix for a iser- > > > target queue-full memory leak: > > > > > > https://www.spinics.net/lists/target-devel/msg16282.html > > > > > > Just curious how frequent this happens in practice with sustained large block > > > workloads, as it appears to effect at least three different iwarp RNICS (i40iw, > > > qedr and iw_cxgb4)..? > > > > > > Is there anything else from an iser-target consumer level that should be > > > changed for iwarp to avoid repeated ib_post_send() failures..? > > > > > Would like to mention, that although we are an iWARP RNIC as well, we've hit this > > Issue when running RoCE. It's not iWARP related. > > This is easily reproduced within seconds with IO size of 5121K > > Using 5 Targets with 2 Ram Disk each and 5 targets with FileIO Disks each. > > > > IO Command used: > > maim -b512k -T32 -t2 -Q8 -M0 -o -u -n -m17 -ftargets.dat -d1 > > > > thanks, > > Michal > > Its seen with block size >= 2M on a single target 1 RAM disk config. And similar to Michals report; > rather quickly, in a matter of seconds. > > fio --rw=read --bs=2048k --numjobs=1 --iodepth=128 --runtime=30 --size=20g --loops=1 --ioengine=libaio > --direct=1 --invalidate=1 --fsync_on_close=1 --norandommap --exitall --filename=/dev/sdb --name=sdb > 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..? That is, if rdma_rw_ctx_post() -> ib_post_send() failures are related to maximum payload size per I/O being too large there is an existing target_core_fabric_ops mechanism for limiting using SCSI residuals, originally utilized by qla2xxx here: target/qla2xxx: Honor max_data_sg_nents I/O transfer limit https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8f9b565482c537821588444e09ff732c7d65ed6e Note this patch also will return a smaller Block Limits VPD (0x86) MAXIMUM TRANSFER LENGTH based on max_data_sg_nents * PAGE_SIZE, which means for modern SCSI initiators honoring MAXIMUM TRANSFER LENGTH will automatically limit maximum outgoing payload transfer length, and avoid SCSI residual logic. As-is, iser-target doesn't a propagate max_data_sg_ents limit into iscsi-target, but you can try testing with a smaller value to see if it's useful. Eg: diff --git a/drivers/target/iscsi/iscsi_target_configfs.c b/drivers/target/iscsi/iscsi_target_configf index 0ebc481..d8a4cc5 100644 --- a/drivers/target/iscsi/iscsi_target_configfs.c +++ b/drivers/target/iscsi/iscsi_target_configfs.c @@ -1553,6 +1553,7 @@ static void lio_release_cmd(struct se_cmd *se_cmd) .module = THIS_MODULE, .name = "iscsi", .node_acl_size = sizeof(struct iscsi_node_acl), + .max_data_sg_nents = 32, /* 32 * PAGE_SIZE = MAXIMUM TRANSFER LENGTH */ .get_fabric_name = iscsi_get_fabric_name, .tpg_get_wwn = lio_tpg_get_endpoint_wwn, .tpg_get_tag = lio_tpg_get_tag, Second, if the failures are not SCSI transfer length specific, another option would be to limit the total command sequence number depth (CmdSN) per session. This is controlled at runtime by default_cmdsn_depth TPG attribute: /sys/kernel/config/target/iscsi/$TARGET_IQN/$TPG/attrib/default_cmdsn_depth and on per initiator context with cmdsn_depth NodeACL attribute: /sys/kernel/config/target/iscsi/$TARGET_IQN/$TPG/acls/$ACL_IQN/cmdsn_depth Note these default to 64, and can be changed at build time via include/target/iscsi/iscsi_target_core.h:TA_DEFAULT_CMDSN_DEPTH. That said, Sagi, any further comments as what else iser-target should be doing to avoid repeated queue-fulls with limited hw sges..? -- 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
