[PATCH for-next 06/20] RDMA/rtrs: Change MAX_SESS_QUEUE_DEPTH

From: Gioh Kim <gi-oh.kim@ionos.com>
To: linux-rdma@vger.kernel.org
Cc: bvanassche@acm.org, leon@kernel.org, dledford@redhat.com,
	jgg@ziepe.ca, haris.iqbal@ionos.com, jinpu.wang@ionos.com,
	Gioh Kim <gi-oh.kim@cloud.ionos.com>,
	Gioh Kim <gi-oh.kim@ionos.com>
Subject: [PATCH for-next 06/20] RDMA/rtrs: Change MAX_SESS_QUEUE_DEPTH
Date: Mon,  3 May 2021 13:48:04 +0200	[thread overview]
Message-ID: <20210503114818.288896-7-gi-oh.kim@ionos.com> (raw)
In-Reply-To: <20210503114818.288896-1-gi-oh.kim@ionos.com>

From: Gioh Kim <gi-oh.kim@cloud.ionos.com>

Max IB immediate data size is 2^28 (MAX_IMM_PAYL_BITS)
and the minimum chunk size is 4096 (2^12).
Therefore the maximum sess_queue_depth is 65536 (2^16).

Signed-off-by: Gioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
---
 drivers/infiniband/ulp/rtrs/rtrs-pri.h | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/infiniband/ulp/rtrs/rtrs-pri.h b/drivers/infiniband/ulp/rtrs/rtrs-pri.h
index bcad5e2168c5..62924ad5362d 100644
--- a/drivers/infiniband/ulp/rtrs/rtrs-pri.h
+++ b/drivers/infiniband/ulp/rtrs/rtrs-pri.h
@@ -47,12 +47,15 @@ enum {
 	MAX_PATHS_NUM = 128,
 
 	/*
-	 * With the size of struct rtrs_permit allocated on the client, 4K
-	 * is the maximum number of rtrs_permits we can allocate. This number is
-	 * also used on the client to allocate the IU for the user connection
-	 * to receive the RDMA addresses from the server.
+	 * Max IB immediate data size is 2^28 (MAX_IMM_PAYL_BITS)
+	 * and the minimum chunk size is 4096 (2^12).
+	 * So the maximum sess_queue_depth is 65536 (2^16) in theory.
+	 * But mempool_create, create_qp and ib_post_send fail with
+	 * "cannot allocate memory" error if sess_queue_depth is too big.
+	 * Therefore the pratical max value of sess_queue_depth is
+	 * somewhere between 1 and 65536 and it depends on the system.
 	 */
-	MAX_SESS_QUEUE_DEPTH = 4096,
+	MAX_SESS_QUEUE_DEPTH = 65536,
 
 	RTRS_HB_INTERVAL_MS = 5000,
 	RTRS_HB_MISSED_MAX = 5,
-- 
2.25.1

