gnu: Add earlyoom-service-type.

* gnu/services/linux.scm: New file.
* tests/services/linux.scm: Add test.
* Makefile.am (SCM_TESTS): Register test.
* doc/guix.texi (Linux Services): Add a new section and document the new
service and its configuration.

1 files changed, 68 insertions, 1 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 3141c4582f..956c25ba9e 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -48,7 +48,7 @@ Copyright @copyright{} 2017 humanitiesNerd@*
 Copyright @copyright{} 2017 Christopher Allan Webber@*
 Copyright @copyright{} 2017, 2018, 2019 Marius Bakke@*
 Copyright @copyright{} 2017, 2019 Hartmut Goebel@*
-Copyright @copyright{} 2017, 2019 Maxim Cournoyer@*
+Copyright @copyright{} 2017, 2019, 2020 Maxim Cournoyer@*
 Copyright @copyright{} 2017, 2018, 2019, 2020 Tobias Geerinckx-Rice@*
 Copyright @copyright{} 2017 George Clemmer@*
 Copyright @copyright{} 2017 Andy Wingo@*
@@ -310,6 +310,7 @@ Services
 * Version Control Services::    Providing remote access to Git repositories.
 * Game Services::               Game servers.
 * PAM Mount Service::           Service to mount volumes when logging in.
+* Linux Services::              Services tied to the Linux kernel.
 * Miscellaneous Services::      Other services.
 
 Defining Services
@@ -12084,6 +12085,7 @@ declaration.
 * Game Services::               Game servers.
 * PAM Mount Service::           Service to mount volumes when logging in.
 * Guix Services::               Services relating specifically to Guix.
+* Linux Services::              Services tied to the Linux kernel.
 * Miscellaneous Services::      Other services.
 @end menu
 
@@ -25129,6 +25131,71 @@ list.
 @end table
 @end deftp
 
+@node Linux Services
+@subsubheading Linux Services
+
+@cindex oom
+@cindex out of memory killer
+@cindex earlyoom
+@cindex early out of memory daemon
+@subsection Early OOM Service
+
+@uref{https://github.com/rfjakob/earlyoom,Early OOM}, also known as
+Earlyoom, is a minimalist out of memory (OOM) daemon that runs in user
+space and provides a more responsive and configurable alternative to the
+in-kernel OOM killer.  It is useful to prevent the system from becoming
+unresponsive when it runs out of memory.
+
+@deffn {Scheme Variable} earlyoom-service-type
+The service type for running @command{earlyoom}, the Early OOM daemon.
+Its value must be a @code{earlyoom-configuration} object, described
+below.  The service can be instantiated in its default configuration
+with:
+
+@lisp
+(service earlyoom-service-type)
+@end lisp
+@end deffn
+
+@deftp {Data Type} earlyoom-configuration
+This is the configuration record for the @code{earlyoom-service-type}.
+
+@table @asis
+@item @code{earlyoom} (default: @var{earlyoom})
+The Earlyoom package to use.
+
+@item @code{minimum-available-memory} (default: @code{10})
+The threshold for the minimum @emph{available} memory, in percentages.
+
+@item @code{minimum-free-swap} (default: @code{10})
+The threshold for the minimum free swap memory, in percentages.
+
+@item @code{prefer-regexp} (default: @code{#f})
+A regular expression (as a string) to match the names of the processes
+that should be preferably killed.
+
+@item @code{avoid-regexp} (default: @code{#f})
+A regular expression (as a string) to match the names of the processes
+that should @emph{not} be killed.
+
+@item @code{memory-report-interval} (default: @code{0})
+The interval in seconds at which a memory report is printed.  It is
+disabled by default.
+
+@item @code{ignore-positive-oom-score-adj?} (default: @code{#f})
+A boolean indicating whether the positive adjustments set in
+@file{/proc/*/oom_score_adj}.
+
+@item @code{show-debug-messages?} (default: @code{#f})
+A boolean indicating whether debug messages should be printed.  The logs
+are saved at @file{/var/log/earlyoom.log}.
+
+@item @code{send-notification-command} (default: @code{#f})
+This can be used to provide a custom command used for sending
+notifications.
+@end table
+@end deftp
+
 
 @node Miscellaneous Services
 @subsection Miscellaneous Services