File s390-tools-sles15sp3-dasd-change-DASD-udev-rule-to-set-none-scheduler.patch of Package s390-tools.23971

Subject: [PATCH] [BZ 192049] udev/dasd: change DASD udev-rule to set none scheduler
From: Stefan Haberland <sth@linux.ibm.com>

Description:   dasd: change default scheduler to reduce CPU consumption
Symptom:       CPU consumption up to 20% higher for mq-deadline
               compared to none scheduler for DASD devices with no
               difference in throughput.
Problem:       Performance analysis showed that with recent DASD
               device drivers using multi-queue block queuing the
               throughput of mq-deadline and none scheduler is nearly
               identical but the CPU consumption of mq-deadline
               scheduler due to its optimizations is up to 20% higher
               compared to none scheduler.
Solution:      Set none scheduler as default in the DASD udev rule.
Reproduction:  Use DASD devices with mq-deadline scheduler.
Upstream-ID:   a65bc51cf4e5c1fe628bb182cc1a02ee83eb102d
Problem-ID:    192049

Upstream-Description:

              udev/dasd: change DASD udev-rule to set none scheduler

              Performance evaluation showed that using the mq-deadline scheduler for DASD
              devices leads to a significantly higher CPU consumption compared to using
              none scheduler while having the same amount of throughput.
              Setting none scheduler as default in the dasd udev rule.

              Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
              Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
              Signed-off-by: Jan Hoeppner <hoeppner@linux.ibm.com>


Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
---
 etc/udev/rules.d/59-dasd.rules |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/etc/udev/rules.d/59-dasd.rules
+++ b/etc/udev/rules.d/59-dasd.rules
@@ -26,10 +26,10 @@
 
 LABEL="dasd_symlinks_end"
 
-# on device add set request queue scheduler to deadline
+# on device add set request queue scheduler to none
 SUBSYSTEM!="block", GOTO="sched_end"
 
 ACTION!="change", GOTO="sched_end"
-KERNEL=="dasd*[!0-9]", TEST=="queue/scheduler", ATTR{queue/scheduler}="deadline"
+KERNEL=="dasd*[!0-9]", TEST=="queue/scheduler", ATTR{queue/scheduler}="none"
 
 LABEL="sched_end"