[PATCH 005/124] staging: lustre: obdclass: optimize busy loop wait

[James Simmons]

From: Alexander Zarochentsev 

two optimizations in the busy loop wait in class_cleanup():
(1) remove unnecessary spinlocks protecting obd_conn_inprogress
access
(2) replace cond_resched by more suitable yield to unconditionally
yield the CPU if the condition check fails.

Signed-off-by: Alexander Zarochentsev 
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5397
Xyratex-bug-id: MRP-1991
Reviewed-on: http://review.whamcloud.com/11198
Reviewed-by: Andreas Dilger 
Reviewed-by: Dmitry Eremin 
Reviewed-by: Oleg Drokin 
Signed-off-by: James Simmons 
---
 .../staging/lustre/lustre/obdclass/obd_config.c|   13 -
 1 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/staging/lustre/lustre/obdclass/obd_config.c 
b/drivers/staging/lustre/lustre/obdclass/obd_config.c
index 036f396..fddfc9c 100644
--- a/drivers/staging/lustre/lustre/obdclass/obd_config.c
+++ b/drivers/staging/lustre/lustre/obdclass/obd_config.c
@@ -414,17 +414,12 @@ static int class_cleanup(struct obd_device *obd, struct 
lustre_cfg *lcfg)
}
/* Leave this on forever */
obd->obd_stopping = 1;
-
-   /* wait for already-arrived-connections to finish. */
-   while (obd->obd_conn_inprogress > 0) {
-   spin_unlock(>obd_dev_lock);
-
-   cond_resched();
-
-   spin_lock(>obd_dev_lock);
-   }
spin_unlock(>obd_dev_lock);
 
+   while (obd->obd_conn_inprogress > 0)
+   yield();
+   smp_rmb();
+
if (lcfg->lcfg_bufcount >= 2 && LUSTRE_CFG_BUFLEN(lcfg, 1) > 0) {
for (flag = lustre_cfg_string(lcfg, 1); *flag != 0; flag++)
switch (*flag) {
-- 
1.7.1

[PATCH 005/124] staging: lustre: obdclass: optimize busy loop wait

[James Simmons]

From: Alexander Zarochentsev 

two optimizations in the busy loop wait in class_cleanup():
(1) remove unnecessary spinlocks protecting obd_conn_inprogress
access
(2) replace cond_resched by more suitable yield to unconditionally
yield the CPU if the condition check fails.

Signed-off-by: Alexander Zarochentsev 
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5397
Xyratex-bug-id: MRP-1991
Reviewed-on: http://review.whamcloud.com/11198
Reviewed-by: Andreas Dilger 
Reviewed-by: Dmitry Eremin 
Reviewed-by: Oleg Drokin 
Signed-off-by: James Simmons 
---
 .../staging/lustre/lustre/obdclass/obd_config.c|   13 -
 1 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/staging/lustre/lustre/obdclass/obd_config.c 
b/drivers/staging/lustre/lustre/obdclass/obd_config.c
index 036f396..fddfc9c 100644
--- a/drivers/staging/lustre/lustre/obdclass/obd_config.c
+++ b/drivers/staging/lustre/lustre/obdclass/obd_config.c
@@ -414,17 +414,12 @@ static int class_cleanup(struct obd_device *obd, struct 
lustre_cfg *lcfg)
}
/* Leave this on forever */
obd->obd_stopping = 1;
-
-   /* wait for already-arrived-connections to finish. */
-   while (obd->obd_conn_inprogress > 0) {
-   spin_unlock(>obd_dev_lock);
-
-   cond_resched();
-
-   spin_lock(>obd_dev_lock);
-   }
spin_unlock(>obd_dev_lock);
 
+   while (obd->obd_conn_inprogress > 0)
+   yield();
+   smp_rmb();
+
if (lcfg->lcfg_bufcount >= 2 && LUSTRE_CFG_BUFLEN(lcfg, 1) > 0) {
for (flag = lustre_cfg_string(lcfg, 1); *flag != 0; flag++)
switch (*flag) {
-- 
1.7.1