diff options
| author | Nicholas Bellinger <nab@linux-iscsi.org> | 2014-01-10 02:06:59 +0000 |
|---|---|---|
| committer | Nicholas Bellinger <nab@linux-iscsi.org> | 2014-01-19 10:59:05 +0000 |
| commit | 4a4caa29f1abcb14377e05d57c0793d338fb945d (patch) | |
| tree | 9aa82f238da7f6dc93d543aa76616bafdfbf552b /drivers/target/iscsi | |
| parent | 49a47f2cafbe4ca3839f8ae99c6fdeffd5fcaf45 (diff) | |
iscsi-target: Pre-allocate more tags to avoid ack starvation
This patch addresses an traditional iscsi-target fabric ack starvation
issue where iscsit_allocate_cmd() -> percpu_ida_alloc_state() ends up
hitting slow path percpu-ida code, because iscsit_ack_from_expstatsn()
is expected to free ack'ed tags after tag allocation.
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.
So that said, this patch bumps up the pre-allocated number of
per session tags to:
(max(queue_depth, ISCSIT_MIN_TAGS) * 2) + ISCSIT_EXTRA_TAGS
for good measure to avoid the percpu_ida_alloc_state() slow path.
Cc: <stable@vger.kernel.org> #3.12+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Diffstat (limited to 'drivers/target/iscsi')
| -rw-r--r-- | drivers/target/iscsi/iscsi_target_nego.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/target/iscsi/iscsi_target_nego.c b/drivers/target/iscsi/iscsi_target_nego.c index 83c965c6538..582ba84075e 100644 --- a/drivers/target/iscsi/iscsi_target_nego.c +++ b/drivers/target/iscsi/iscsi_target_nego.c @@ -1192,7 +1192,7 @@ get_target: */ alloc_tags: tag_num = max_t(u32, ISCSIT_MIN_TAGS, queue_depth); - tag_num += (tag_num / 2) + 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); |