gnu: Add powertop-service-type.

* gnu/services/pm.scm (powertop-shepherd-service)
(powertop-service-type, powertop-configuration): New variables.
* doc/guix.texi (Power Management Services): Document powertop-service-type.

Change-Id: I1c5ef855526458ad54f62ca6e755da82acce1c4a
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

doc/guix.texi

@@ -35800,6 +35800,32 @@ Ignore cpuid check for supported CPU models.
 @item @code{thermald} (default: @var{thermald})
 Package object of thermald.
 
+@cindex PowerTOP
+@cindex power consumption tuning with PowerTOP
+@subsubheading PowerTOP
+
+The @code{(gnu services pm)} module also provides a service definition
+for @uref{https://01.org/powertop/, PowerTOP}, a power consumption
+analysis and tuning tool.  When started, it tunes Linux kernel settings
+to reduce power consumption.
+
+@defvar powertop-service-type
+The service type for PowerTOP.  No configuration is necessary.  When the
+service starts, it executes @code{powertop --auto-tune}.
+
+@lisp
+(service powertop-service-type)
+@end lisp
+@end defvar
+
+Available @code{powertop-configuration} fields are:
+
+@deftypevr {@code{powertop-configuration} parameter} package powertop
+The PowerTOP package.  Defaults to @code{powertop} in the @code{(gnu
+packages linux)} module
+
+@end deftypevr
+
 @end table
 @end deftp
 

gnu/services/pm.scm

@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
 ;;; Copyright © 2024 Dariqq <dariqq@posteo.net>
+;;; Copyright © 2024 Ian Eure <ian@retrospec.tv>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -18,6 +19,8 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (gnu services pm)
+  #:use-module (srfi srfi-1)
+  #:use-module (ice-9 match)
   #:use-module (guix gexp)
   #:use-module (guix packages)
   #:use-module (guix records)
@@ -37,7 +40,10 @@ (define-module (gnu services pm)
             tlp-configuration
 
             thermald-configuration
-            thermald-service-type))
+            thermald-service-type
+
+            powertop-configuration
+            powertop-service-type))
 
 ;;;
 ;;; power-profiles-daemon
@@ -525,3 +531,37 @@ (define thermald-service-type
    (default-value (thermald-configuration))
    (description "Run thermald, a CPU frequency scaling service that helps
 prevent overheating.")))
+
+
+
+;;;
+;;; powertop
+;;;
+;;; Calls `powertop --auto-tune' to reduce energy consumption.
+
+(define-configuration powertop-configuration
+  (powertop (package powertop) "PowerTOP package to use."))
+
+(define powertop-shepherd-service
+  (match-lambda
+    (($ <powertop-configuration> powertop)
+     (shepherd-service
+      (documentation "Tune kernel power settings at boot.")
+      (provision '(powertop powertop-auto-tune))
+      (requirement '(user-processes))
+      (one-shot? #t)
+      (start #~(lambda _
+                 (zero? (system* #$(file-append powertop "/sbin/powertop")
+                                 "--auto-tune"))))))))
+
+(define powertop-service-type
+  (service-type
+   (name 'powertop)
+   (extensions
+    (list
+     (service-extension shepherd-root-service-type
+                        (compose list powertop-shepherd-service))))
+   (compose concatenate)
+   (default-value (powertop-configuration))
+   (description "Tune power-related kernel parameters to reduce energy
+ consumption.")))