Re: [PATCH v3] target: Drop iSCSI use of mutex around max_cmd_sn increment

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

On Thu, 2015-07-23 at 14:53 -0700, Spencer Baugh wrote:
> From: Roland Dreier <roland@purestorage.com>
> 
> 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.
> 
> v2: Get correct values for logging
> v3: Fix whitespace damage
> 
> Signed-off-by: Roland Dreier <roland@purestorage.com>
> Signed-off-by: Spencer Baugh <sbaugh@catern.com>
> ---
>  drivers/target/iscsi/iscsi_target.c          | 18 +++++++++---------
>  drivers/target/iscsi/iscsi_target_configfs.c |  6 ++++--
>  drivers/target/iscsi/iscsi_target_device.c   |  7 ++-----
>  drivers/target/iscsi/iscsi_target_login.c    |  2 +-
>  drivers/target/iscsi/iscsi_target_nego.c     |  9 +++------
>  drivers/target/iscsi/iscsi_target_tmr.c      |  2 +-
>  drivers/target/iscsi/iscsi_target_util.c     |  7 ++++---
>  include/target/iscsi/iscsi_target_core.h     |  2 +-
>  8 files changed, 25 insertions(+), 28 deletions(-)
> 

A nice optimization for iscsi-target + ib_isert on this patch.

Applied to target-pending/for-next. 

Thanks Roland & Co.