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Commit 95b60f07 authored by Nicholas Bellinger's avatar Nicholas Bellinger
Browse files

ib_isert: Add support for completion interrupt coalescing 



This patch adds support for completion interrupt coalescing that
allows only every ISERT_COMP_BATCH_COUNT (8) to set IB_SEND_SIGNALED,
thus avoiding completion interrupts for every posted iser_tx_desc.

The batch processing is done using a per isert_conn llist that once
IB_SEND_SIGNALED has been set is saved to tx_desc->comp_llnode_batch,
and completion processing of previously posted iser_tx_descs is done
in a single shot from within isert_send_completion() code.

Note this is only done for response PDUs from ISCSI_OP_SCSI_CMD, and
all other control type of PDU responses will force an implicit batch
drain to occur.

Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Roland Dreier <roland@purestorage.com>
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent 2dd1d53f

drivers/infiniband/ulp/isert/ib_isert.c

+51 −12
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <linux/socket.h>

#include <linux/in.h>

#include <linux/in6.h>

#include <linux/llist.h>

#include <rdma/ib_verbs.h>

#include <rdma/rdma_cm.h>

#include <target/target_core_base.h>
@@ -489,6 +490,7 @@ isert_connect_request(struct rdma_cm_id *cma_id, struct rdma_cm_event *event) 
	kref_init(&isert_conn->conn_kref);

	kref_get(&isert_conn->conn_kref);

	mutex_init(&isert_conn->conn_mutex);

	mutex_init(&isert_conn->conn_comp_mutex);

	spin_lock_init(&isert_conn->conn_lock);



	cma_id->context = isert_conn;
@@ -843,14 +845,32 @@ isert_init_tx_hdrs(struct isert_conn *isert_conn, 
}



static void

isert_init_send_wr(struct isert_cmd *isert_cmd, struct ib_send_wr *send_wr)

isert_init_send_wr(struct isert_conn *isert_conn, struct isert_cmd *isert_cmd,

		   struct ib_send_wr *send_wr, bool coalesce)

{

	struct iser_tx_desc *tx_desc = &isert_cmd->tx_desc;



	isert_cmd->rdma_wr.iser_ib_op = ISER_IB_SEND;

	send_wr->wr_id = (unsigned long)&isert_cmd->tx_desc;

	send_wr->opcode = IB_WR_SEND;

	send_wr->send_flags = IB_SEND_SIGNALED;

	send_wr->sg_list = &isert_cmd->tx_desc.tx_sg[0];

	send_wr->sg_list = &tx_desc->tx_sg[0];

	send_wr->num_sge = isert_cmd->tx_desc.num_sge;

	/*

	 * Coalesce send completion interrupts by only setting IB_SEND_SIGNALED

	 * bit for every ISERT_COMP_BATCH_COUNT number of ib_post_send() calls.

	 */

	mutex_lock(&isert_conn->conn_comp_mutex);

	if (coalesce &&

	    ++isert_conn->conn_comp_batch < ISERT_COMP_BATCH_COUNT) {

		llist_add(&tx_desc->comp_llnode, &isert_conn->conn_comp_llist);

		mutex_unlock(&isert_conn->conn_comp_mutex);

		return;

	}

	isert_conn->conn_comp_batch = 0;

	tx_desc->comp_llnode_batch = llist_del_all(&isert_conn->conn_comp_llist);

	mutex_unlock(&isert_conn->conn_comp_mutex);



	send_wr->send_flags = IB_SEND_SIGNALED;

}



static int
@@ -1582,7 +1602,7 @@ isert_response_completion(struct iser_tx_desc *tx_desc, 
}



static void

isert_send_completion(struct iser_tx_desc *tx_desc,

__isert_send_completion(struct iser_tx_desc *tx_desc,

		        struct isert_conn *isert_conn)

{

	struct ib_device *ib_dev = isert_conn->conn_cm_id->device;
@@ -1623,6 +1643,24 @@ isert_send_completion(struct iser_tx_desc *tx_desc, 
	}

}



static void

isert_send_completion(struct iser_tx_desc *tx_desc,

		      struct isert_conn *isert_conn)

{

	struct llist_node *llnode = tx_desc->comp_llnode_batch;

	struct iser_tx_desc *t;

	/*

	 * Drain coalesced completion llist starting from comp_llnode_batch

	 * setup in isert_init_send_wr(), and then complete trailing tx_desc.

	 */

	while (llnode) {

		t = llist_entry(llnode, struct iser_tx_desc, comp_llnode);

		llnode = llist_next(llnode);

		__isert_send_completion(t, isert_conn);

	}

	__isert_send_completion(tx_desc, isert_conn);

}



static void

isert_cq_comp_err(struct iser_tx_desc *tx_desc, struct isert_conn *isert_conn)

{
@@ -1793,7 +1831,7 @@ isert_put_response(struct iscsi_conn *conn, struct iscsi_cmd *cmd) 
		isert_cmd->tx_desc.num_sge = 2;

	}



	isert_init_send_wr(isert_cmd, send_wr);

	isert_init_send_wr(isert_conn, isert_cmd, send_wr, true);



	pr_debug("Posting SCSI Response IB_WR_SEND >>>>>>>>>>>>>>>>>>>>>>\n");
@@ -1813,7 +1851,7 @@ isert_put_nopin(struct iscsi_cmd *cmd, struct iscsi_conn *conn, 
			       &isert_cmd->tx_desc.iscsi_header,

			       nopout_response);

	isert_init_tx_hdrs(isert_conn, &isert_cmd->tx_desc);

	isert_init_send_wr(isert_cmd, send_wr);

	isert_init_send_wr(isert_conn, isert_cmd, send_wr, false);



	pr_debug("Posting NOPIN Response IB_WR_SEND >>>>>>>>>>>>>>>>>>>>>>\n");
@@ -1831,7 +1869,7 @@ isert_put_logout_rsp(struct iscsi_cmd *cmd, struct iscsi_conn *conn) 
	iscsit_build_logout_rsp(cmd, conn, (struct iscsi_logout_rsp *)

				&isert_cmd->tx_desc.iscsi_header);

	isert_init_tx_hdrs(isert_conn, &isert_cmd->tx_desc);

	isert_init_send_wr(isert_cmd, send_wr);

	isert_init_send_wr(isert_conn, isert_cmd, send_wr, false);



	pr_debug("Posting Logout Response IB_WR_SEND >>>>>>>>>>>>>>>>>>>>>>\n");
@@ -1849,7 +1887,7 @@ isert_put_tm_rsp(struct iscsi_cmd *cmd, struct iscsi_conn *conn) 
	iscsit_build_task_mgt_rsp(cmd, conn, (struct iscsi_tm_rsp *)

				  &isert_cmd->tx_desc.iscsi_header);

	isert_init_tx_hdrs(isert_conn, &isert_cmd->tx_desc);

	isert_init_send_wr(isert_cmd, send_wr);

	isert_init_send_wr(isert_conn, isert_cmd, send_wr, false);



	pr_debug("Posting Task Management Response IB_WR_SEND >>>>>>>>>>>>>>>>>>>>>>\n");
@@ -1881,7 +1919,7 @@ isert_put_reject(struct iscsi_cmd *cmd, struct iscsi_conn *conn) 
	tx_dsg->lkey	= isert_conn->conn_mr->lkey;

	isert_cmd->tx_desc.num_sge = 2;



	isert_init_send_wr(isert_cmd, send_wr);

	isert_init_send_wr(isert_conn, isert_cmd, send_wr, false);



	pr_debug("Posting Reject IB_WR_SEND >>>>>>>>>>>>>>>>>>>>>>\n");
@@ -1921,7 +1959,7 @@ isert_put_text_rsp(struct iscsi_cmd *cmd, struct iscsi_conn *conn) 
		tx_dsg->lkey	= isert_conn->conn_mr->lkey;

		isert_cmd->tx_desc.num_sge = 2;

	}

	isert_init_send_wr(isert_cmd, send_wr);

	isert_init_send_wr(isert_conn, isert_cmd, send_wr, false);



	pr_debug("Posting Text Response IB_WR_SEND >>>>>>>>>>>>>>>>>>>>>>\n");
@@ -2309,7 +2347,8 @@ isert_put_datain(struct iscsi_conn *conn, struct iscsi_cmd *cmd) 
	iscsit_build_rsp_pdu(cmd, conn, false, (struct iscsi_scsi_rsp *)

			     &isert_cmd->tx_desc.iscsi_header);

	isert_init_tx_hdrs(isert_conn, &isert_cmd->tx_desc);

	isert_init_send_wr(isert_cmd, &isert_cmd->tx_desc.send_wr);

	isert_init_send_wr(isert_conn, isert_cmd,

			   &isert_cmd->tx_desc.send_wr, true);



	atomic_inc(&isert_conn->post_send_buf_count);

drivers/infiniband/ulp/isert/ib_isert.h

+6 −0
Original line number Diff line number Diff line
@@ -43,6 +43,8 @@ struct iser_tx_desc { 
	struct ib_sge	tx_sg[2];

	int		num_sge;

	struct isert_cmd *isert_cmd;

	struct llist_node *comp_llnode_batch;

	struct llist_node comp_llnode;

	struct ib_send_wr send_wr;

} __packed;
@@ -121,6 +123,10 @@ struct isert_conn { 
	int			conn_frwr_pool_size;

	/* lock to protect frwr_pool */

	spinlock_t		conn_lock;

#define ISERT_COMP_BATCH_COUNT	8

	int			conn_comp_batch;

	struct llist_head	conn_comp_llist;

	struct mutex		conn_comp_mutex;

};



#define ISERT_MAX_CQ 64