diff options
| author | Roland Dreier <roland@purestorage.com> | 2015-07-24 00:53:32 +0300 |
|---|---|---|
| committer | Nicholas Bellinger <nab@linux-iscsi.org> | 2015-08-03 09:11:52 +0300 |
| commit | 109e2381749c1cfd94a0d22b2b54142539024973 (patch) | |
| tree | 9695ecd3738a7bad43edcca4eb641339e7a30060 /drivers/target/iscsi/iscsi_target_device.c | |
| parent | 24c7d6c7316c72301bf8ecfc1189fd476176fd75 (diff) | |
| download | linux-109e2381749c1cfd94a0d22b2b54142539024973.tar.xz | |
target: Drop iSCSI use of mutex around max_cmd_sn increment
In a performance profile, taking a mutex in iscsit_increment_maxcmdsn()
shows up very high. However taking a mutex around "sess->max_cmd_sn += 1"
seems pretty silly: we're not serializing against other contexts in
any useful way.
I did a quick audit and there don't appear to be any other places that
use max_cmd_sn within the mutex more than once, so this lock can't be
providing any useful serialization.
(Get correct values for logging - fix whitespace damage)
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Spencer Baugh <sbaugh@catern.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Diffstat (limited to 'drivers/target/iscsi/iscsi_target_device.c')
| -rw-r--r-- | drivers/target/iscsi/iscsi_target_device.c | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/drivers/target/iscsi/iscsi_target_device.c b/drivers/target/iscsi/iscsi_target_device.c index 5fabcd3d623f..07d2ef67dba6 100644 --- a/drivers/target/iscsi/iscsi_target_device.c +++ b/drivers/target/iscsi/iscsi_target_device.c @@ -47,7 +47,7 @@ void iscsit_determine_maxcmdsn(struct iscsi_session *sess) * core_set_queue_depth_for_node(). */ sess->cmdsn_window = se_nacl->queue_depth; - sess->max_cmd_sn = (sess->max_cmd_sn + se_nacl->queue_depth) - 1; + atomic_set(&sess->max_cmd_sn, (u32) atomic_read(&sess->max_cmd_sn) + se_nacl->queue_depth - 1); } void iscsit_increment_maxcmdsn(struct iscsi_cmd *cmd, struct iscsi_session *sess) @@ -57,9 +57,6 @@ void iscsit_increment_maxcmdsn(struct iscsi_cmd *cmd, struct iscsi_session *sess cmd->maxcmdsn_inc = 1; - mutex_lock(&sess->cmdsn_mutex); - sess->max_cmd_sn += 1; - pr_debug("Updated MaxCmdSN to 0x%08x\n", sess->max_cmd_sn); - mutex_unlock(&sess->cmdsn_mutex); + pr_debug("Updated MaxCmdSN to 0x%08x\n", atomic_inc_return(&sess->max_cmd_sn)); } EXPORT_SYMBOL(iscsit_increment_maxcmdsn); |