svn commit: r282110 - head/etc/defaults

[Adrian Chadd]

Author: adrian
Date: Mon Apr 27 19:18:51 2015
New Revision: 282110
URL: https://svnweb.freebsd.org/changeset/base/282110

Log:
  Drop the default for performance_cx_lowest (ie, what to use when AC is connected) to ACPI C2.
  
  ACPI C3 ends up doing a lot more work before entering sleep, some of which
  requires grabbing a global ACPI hardware serialising mutex.
  
  Because of this, the more CPU cores you have, the more that lock contends
  under load, reaching close to the #1 lock contention (after VM, which is being
  worked on.)
  
  Tested:
  
  * Sandy bridge Xeon, 2 socket * 8 core
  * Ivy bridge Xeon v2, 2 socket * 8 core
  * Westmere-EX, 4 socket * 10 core
  * Ivybridge desktop
  * Sandybridge mobile
  * Ivybridge mobile
  
  MFC after:	2 weeks

Modified:
  head/etc/defaults/rc.conf

Modified: head/etc/defaults/rc.conf
==============================================================================
--- head/etc/defaults/rc.conf	Mon Apr 27 18:41:31 2015	(r282109)
+++ head/etc/defaults/rc.conf	Mon Apr 27 19:18:51 2015	(r282110)
@@ -648,7 +648,7 @@ devfs_system_ruleset=""	# The name (NOT 
 devfs_set_rulesets=""	# A list of /mount/dev=ruleset_name settings to
 			# apply (must be mounted already, i.e. fstab(5))
 devfs_load_rulesets="YES"	# Enable to always load the default rulesets
-performance_cx_lowest="Cmax"	# Online CPU idle state
+performance_cx_lowest="C2"	# Online CPU idle state
 performance_cpu_freq="NONE"	# Online CPU frequency
 economy_cx_lowest="Cmax"	# Offline CPU idle state
 economy_cpu_freq="NONE"		# Offline CPU frequency