Commit dc3b66a0 authored by Gioh Kim's avatar Gioh Kim Committed by Jason Gunthorpe
Browse files

RDMA/rtrs-clt: Add a minimum latency multipath policy 

This patch adds new multipath policy: min-latency.  Client checks the
latency of each path when it sends the heart-beat.  And it sends IO to the
path with the minimum latency.

Link: https://lore.kernel.org/r/20210407113444.150961-2-gi-oh.kim@ionos.com


Signed-off-by: default avatarGioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: default avatarJack Wang <jinpu.wang@ionos.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
parent fe73f96e

drivers/infiniband/ulp/rtrs/rtrs-clt-sysfs.c

+16 −3
Original line number Diff line number Diff line
@@ -101,6 +101,9 @@ static ssize_t mpath_policy_show(struct device *dev, 
	case MP_POLICY_MIN_INFLIGHT:

		return sysfs_emit(page, "min-inflight (MI: %d)\n",

				  clt->mp_policy);

	case MP_POLICY_MIN_LATENCY:

		return sysfs_emit(page, "min-latency (ML: %d)\n",

				  clt->mp_policy);

	default:

		return sysfs_emit(page, "Unknown (%d)\n", clt->mp_policy);

	}
@@ -114,22 +117,32 @@ static ssize_t mpath_policy_store(struct device *dev, 
	struct rtrs_clt *clt;

	int value;

	int ret;

	size_t len = 0;



	clt = container_of(dev, struct rtrs_clt, dev);



	ret = kstrtoint(buf, 10, &value);

	if (!ret && (value == MP_POLICY_RR ||

		     value == MP_POLICY_MIN_INFLIGHT)) {

		     value == MP_POLICY_MIN_INFLIGHT ||

		     value == MP_POLICY_MIN_LATENCY)) {

		clt->mp_policy = value;

		return count;

	}



	/* distinguish "mi" and "min-latency" with length */

	len = strnlen(buf, NAME_MAX);

	if (buf[len - 1] == '\n')

		len--;



	if (!strncasecmp(buf, "round-robin", 11) ||

	    !strncasecmp(buf, "rr", 2))

	    (len == 2 && !strncasecmp(buf, "rr", 2)))

		clt->mp_policy = MP_POLICY_RR;

	else if (!strncasecmp(buf, "min-inflight", 12) ||

		 !strncasecmp(buf, "mi", 2))

		 (len == 2 && !strncasecmp(buf, "mi", 2)))

		clt->mp_policy = MP_POLICY_MIN_INFLIGHT;

	else if (!strncasecmp(buf, "min-latency", 11) ||

		 (len == 2 && !strncasecmp(buf, "ml", 2)))

		clt->mp_policy = MP_POLICY_MIN_LATENCY;

	else

		return -EINVAL;

drivers/infiniband/ulp/rtrs/rtrs-clt.c

+56 −1
Original line number Diff line number Diff line
@@ -628,6 +628,8 @@ static void rtrs_clt_rdma_done(struct ib_cq *cq, struct ib_wc *wc) 
		} else if (imm_type == RTRS_HB_ACK_IMM) {

			WARN_ON(con->c.cid);

			sess->s.hb_missed_cnt = 0;

			sess->s.hb_cur_latency =

				ktime_sub(ktime_get(), sess->s.hb_last_sent);

			if (sess->flags & RTRS_MSG_NEW_RKEY_F)

				return  rtrs_clt_recv_done(con, wc);

		} else {
@@ -826,6 +828,57 @@ static struct rtrs_clt_sess *get_next_path_min_inflight(struct path_it *it) 
	return min_path;

}



/**

 * get_next_path_min_latency() - Returns path with minimal latency.

 * @it:	the path pointer

 *

 * Return: a path with the lowest latency or NULL if all paths are tried

 *

 * Locks:

 *    rcu_read_lock() must be hold.

 *

 * Related to @MP_POLICY_MIN_LATENCY

 *

 * This DOES skip an already-tried path.

 * There is a skip-list to skip a path if the path has tried but failed.

 * It will try the minimum latency path and then the second minimum latency

 * path and so on. Finally it will return NULL if all paths are tried.

 * Therefore the caller MUST check the returned

 * path is NULL and trigger the IO error.

 */

static struct rtrs_clt_sess *get_next_path_min_latency(struct path_it *it)

{

	struct rtrs_clt_sess *min_path = NULL;

	struct rtrs_clt *clt = it->clt;

	struct rtrs_clt_sess *sess;

	ktime_t min_latency = INT_MAX;

	ktime_t latency;



	list_for_each_entry_rcu(sess, &clt->paths_list, s.entry) {

		if (unlikely(READ_ONCE(sess->state) != RTRS_CLT_CONNECTED))

			continue;



		if (unlikely(!list_empty(raw_cpu_ptr(sess->mp_skip_entry))))

			continue;



		latency = sess->s.hb_cur_latency;



		if (latency < min_latency) {

			min_latency = latency;

			min_path = sess;

		}

	}



	/*

	 * add the path to the skip list, so that next time we can get

	 * a different one

	 */

	if (min_path)

		list_add(raw_cpu_ptr(min_path->mp_skip_entry), &it->skip_list);



	return min_path;

}



static inline void path_it_init(struct path_it *it, struct rtrs_clt *clt)

{

	INIT_LIST_HEAD(&it->skip_list);
@@ -834,8 +887,10 @@ static inline void path_it_init(struct path_it *it, struct rtrs_clt *clt) 


	if (clt->mp_policy == MP_POLICY_RR)

		it->next_path = get_next_path_rr;

	else

	else if (clt->mp_policy == MP_POLICY_MIN_INFLIGHT)

		it->next_path = get_next_path_min_inflight;

	else

		it->next_path = get_next_path_min_latency;

}



static inline void path_it_deinit(struct path_it *it)

drivers/infiniband/ulp/rtrs/rtrs-clt.h

+1 −0
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ enum rtrs_clt_state { 
enum rtrs_mp_policy {

	MP_POLICY_RR,

	MP_POLICY_MIN_INFLIGHT,

	MP_POLICY_MIN_LATENCY,

};



/* see Documentation/ABI/testing/sysfs-class-rtrs-client for details */

drivers/infiniband/ulp/rtrs/rtrs-pri.h

+2 −0
Original line number Diff line number Diff line
@@ -112,6 +112,8 @@ struct rtrs_sess { 
	unsigned int		hb_interval_ms;

	unsigned int		hb_missed_cnt;

	unsigned int		hb_missed_max;

	ktime_t			hb_last_sent;

	ktime_t			hb_cur_latency;

};



/* rtrs information unit */

drivers/infiniband/ulp/rtrs/rtrs.c

+3 −0
Original line number Diff line number Diff line
@@ -337,6 +337,9 @@ static void hb_work(struct work_struct *work) 
		schedule_hb(sess);

		return;

	}



	sess->hb_last_sent = ktime_get();



	imm = rtrs_to_imm(RTRS_HB_MSG_IMM, 0);

	err = rtrs_post_rdma_write_imm_empty(usr_con, sess->hb_cqe, imm,

					     0, NULL);