Add oom-score-adj configuration option to control Linux OOM killer. (#1690)

Add Linux kernel OOM killer control option.

This adds the ability to control the Linux OOM killer oom_score_adj
parameter for all Redis processes, depending on the process role (i.e.
master, replica, background child).

A oom-score-adj global boolean flag control this feature. In addition,
specific values can be configured using oom-score-adj-values if
additional tuning is required.

1 files changed, 26 insertions, 0 deletions

diff --git a/redis.conf b/redis.conf
index b8134e8c4..35ee752e1 100644
--- a/redis.conf
+++ b/redis.conf
@@ -1049,6 +1049,32 @@ lazyfree-lazy-user-del no
 # --threads option to match the number of Redis theads, otherwise you'll not
 # be able to notice the improvements.
 
+############################ KERNEL OOM CONTROL ##############################
+
+# On Linux, it is possible to hint the kernel OOM killer on what processes
+# should be killed first when out of memory.
+#
+# Enabling this feature makes Redis actively control the oom_score_adj value
+# for all its processes, depending on their role. The default scores will
+# attempt to have background child processes killed before all others, and
+# replicas killed before masters.
+
+oom-score-adj no
+
+# When oom-score-adj is used, this directive controls the specific values used
+# for master, replica and background child processes. Values range -1000 to
+# 1000 (higher means more likely to be killed).
+#
+# Unprivileged processes (not root, and without CAP_SYS_RESOURCE capabilities)
+# can freely increase their value, but not decrease it below its initial
+# settings.
+#
+# Values are used relative to the initial value of oom_score_adj when the server
+# starts. Because typically the initial value is 0, they will often match the
+# absolute values.
+
+oom-score-adj-values 0 200 800
+
 ############################## APPEND ONLY MODE ###############################
 
 # By default Redis asynchronously dumps the dataset on disk. This mode is