[DragonFlyBSD - Bug #2828] On AMD APUs and Bulldozer CPUs, the machdep.cpu_idle_hlt sysctl should be 3 by default

bugtracker-admin at leaf.dragonflybsd.org bugtracker-admin at leaf.dragonflybsd.org
Thu Jul 23 15:00:05 PDT 2015


Issue #2828 has been updated by dillon.


Hmm.  Did you measure the actual power consumption?  The default (2) is supposed to be a hybrid approach that falls into ACPI.  But looking at it, it is quite possible that the code in kern/lwkt_thread.c that is responsible for resetting gd_idle_repeat to 0 is breaking the concept.

-Matt

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Bug #2828: On AMD APUs and Bulldozer CPUs, the machdep.cpu_idle_hlt sysctl should be 3 by default
http://bugs.dragonflybsd.org/issues/2828#change-12694

* Author: vadaszi
* Status: New
* Priority: High
* Assignee: vadaszi
* Category: Kernel
* Target version: 4.2.x
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Power usage of a default install is unnecessarily high on current AMD CPUs. Setting the default value of the machdep.cpu_idle_hlt sysctl on these CPUs to 3 by default allows for significant power savings.

I'm not sure how setting machdep.cpu_idle_hlt=3 affects power usage on AMD Family 10h CPUs (e.g. Phenom CPUs).

Some quick benchmarking should be done if possible, to compare the performance difference.



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