Commit 434dda42 authored by Sergey Gorenko's avatar Sergey Gorenko Committed by Doug Ledford
Browse files

IB/iser: Do not reduce max_sectors 



The iSER driver reduces max_sectors. For example, if you load the
ib_iser module with max_sectors=1024, you will see that
/sys/class/block/<bdev>/queue/max_hw_sectors_kb is 508. It is an
incorrect value. The expected value is (max_sectors * sector_size) /
1024 = 512.

Reducing of max_sectors can cause performance degradation due to
unnecessary splitting of IO requests.

The number of pages per MR has been fixed here, so there is no longer
any need to reduce max_sectors.

Fixes: 9c674815 ("IB/iser: Fix max_sectors calculation")
Signed-off-by: default avatarSergey Gorenko <sergeygo@mellanox.com>
Reviewed-by: default avatarIsrael Rukshin <israelr@mellanox.com>
Reviewed-by: default avatarMax Gurtovoy <maxg@mellanox.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
Acked-by: default avatarSagi Grimberg <sagi@grimberg.me>
Signed-off-by: default avatarDoug Ledford <dledford@redhat.com>
parent 01298c0c

drivers/infiniband/ulp/iser/iscsi_iser.c

+5 −7
Original line number Diff line number Diff line
@@ -665,19 +665,17 @@ iscsi_iser_session_create(struct iscsi_endpoint *ep, 
			goto free_host;

	}



	/*

	 * FRs or FMRs can only map up to a (device) page per entry, but if the

	 * first entry is misaligned we'll end up using using two entries

	 * (head and tail) for a single page worth data, so we have to drop

	 * one segment from the calculation.

	 */

	max_fr_sectors = ((shost->sg_tablesize - 1) * PAGE_SIZE) >> 9;

	max_fr_sectors = (shost->sg_tablesize * PAGE_SIZE) >> 9;

	shost->max_sectors = min(iser_max_sectors, max_fr_sectors);



	iser_dbg("iser_conn %p, sg_tablesize %u, max_sectors %u\n",

		 iser_conn, shost->sg_tablesize,

		 shost->max_sectors);



	if (shost->max_sectors < iser_max_sectors)

		iser_warn("max_sectors was reduced from %u to %u\n",

			  iser_max_sectors, shost->max_sectors);



	if (cmds_max > max_cmds) {

		iser_info("cmds_max changed from %u to %u\n",

			  cmds_max, max_cmds);

drivers/infiniband/ulp/iser/iscsi_iser.h

+2 −0
Original line number Diff line number Diff line
@@ -498,6 +498,7 @@ struct ib_conn { 
 * @rx_descs:         rx buffers array (cyclic buffer)

 * @num_rx_descs:     number of rx descriptors

 * @scsi_sg_tablesize: scsi host sg_tablesize

 * @pages_per_mr:     maximum pages available for registration

 */

struct iser_conn {

	struct ib_conn		     ib_conn;
@@ -520,6 +521,7 @@ struct iser_conn { 
	struct iser_rx_desc	     *rx_descs;

	u32                          num_rx_descs;

	unsigned short               scsi_sg_tablesize;

	unsigned short               pages_per_mr;

	bool			     snd_w_inv;

};

drivers/infiniband/ulp/iser/iser_initiator.c

+1 −1
Original line number Diff line number Diff line
@@ -251,7 +251,7 @@ int iser_alloc_rx_descriptors(struct iser_conn *iser_conn, 
	iser_conn->min_posted_rx = iser_conn->qp_max_recv_dtos >> 2;



	if (device->reg_ops->alloc_reg_res(ib_conn, session->scsi_cmds_max,

					   iser_conn->scsi_sg_tablesize))

					   iser_conn->pages_per_mr))

		goto create_rdma_reg_res_failed;



	if (iser_alloc_login_buf(iser_conn))

drivers/infiniband/ulp/iser/iser_verbs.c

+18 −3
Original line number Diff line number Diff line
@@ -703,19 +703,34 @@ iser_calc_scsi_params(struct iser_conn *iser_conn, 
		      unsigned int max_sectors)

{

	struct iser_device *device = iser_conn->ib_conn.device;

	struct ib_device_attr *attr = &device->ib_device->attrs;

	unsigned short sg_tablesize, sup_sg_tablesize;

	unsigned short reserved_mr_pages;



	/*

	 * FRs without SG_GAPS or FMRs can only map up to a (device) page per

	 * entry, but if the first entry is misaligned we'll end up using two

	 * entries (head and tail) for a single page worth data, so one

	 * additional entry is required.

	 */

	if ((attr->device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS) &&

	    (attr->device_cap_flags & IB_DEVICE_SG_GAPS_REG))

		reserved_mr_pages = 0;

	else

		reserved_mr_pages = 1;



	sg_tablesize = DIV_ROUND_UP(max_sectors * 512, SIZE_4K);

	if (device->ib_device->attrs.device_cap_flags &

			IB_DEVICE_MEM_MGT_EXTENSIONS)

	if (attr->device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS)

		sup_sg_tablesize =

			min_t(

			 uint, ISCSI_ISER_MAX_SG_TABLESIZE,

			 device->ib_device->attrs.max_fast_reg_page_list_len);

			 attr->max_fast_reg_page_list_len - reserved_mr_pages);

	else

		sup_sg_tablesize = ISCSI_ISER_MAX_SG_TABLESIZE;



	iser_conn->scsi_sg_tablesize = min(sg_tablesize, sup_sg_tablesize);

	iser_conn->pages_per_mr =

		iser_conn->scsi_sg_tablesize + reserved_mr_pages;

}



/**

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