iscsi-target; Allow an extra tag_num / 2 number of percpu_ida tags
This patch bumps the default number of tags allocated per session by
iscsi-target via transport_alloc_session_tags() -> percpu_ida_init()
by another (tag_num / 2).
This is done to take into account the tags waiting to be acknowledged
and released in iscsit_ack_from_expstatsn(), but who's number are not
directly limited by the CmdSN Window queue_depth being enforced by
the target.
Using a larger value here is also useful to prevent percpu_ida_alloc()
from having to steal tags from other CPUs when no tags are available
on the local CPU, while waiting for unacknowledged tags to be released.
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/iscsi/iscsi_target_nego.c b/drivers/target/iscsi/iscsi_target_nego.c
index 14d1aed5..ef6d836 100644
--- a/drivers/target/iscsi/iscsi_target_nego.c
+++ b/drivers/target/iscsi/iscsi_target_nego.c
@@ -1192,7 +1192,7 @@
*/
alloc_tags:
tag_num = max_t(u32, ISCSIT_MIN_TAGS, queue_depth);
- tag_num += ISCSIT_EXTRA_TAGS;
+ tag_num += (tag_num / 2) + ISCSIT_EXTRA_TAGS;
tag_size = sizeof(struct iscsi_cmd) + conn->conn_transport->priv_size;
ret = transport_alloc_session_tags(sess->se_sess, tag_num, tag_size);
