diff --git a/elasticsearch/README.md b/elasticsearch/README.md
index 73522bd2..acdd1552 100644
--- a/elasticsearch/README.md
+++ b/elasticsearch/README.md
@@ -18,7 +18,9 @@ Tasks are extracted in several files, included in `tasks/main.yml` :
 * `elasticsearch_node_name`: node name, defaults to hostname ;
 * `elasticsearch_network_host`: which interfaces to bind to ;
 * `elasticsearch_network_publish_host`: which interface to publish ;
-* `elasticsearch_custom_datadir`: custom datadir
-* `elasticsearch_custom_tmpdir`: custom tmpdir
+* `elasticsearch_custom_datadir`: custom datadir ;
+* `elasticsearch_custom_tmpdir`: custom tmpdir ;
+* `elasticsearch_jvm_xms`: mininum heap size reserved for the JVM (defaults to 2g).
+* `elasticsearch_jvm_xmx`: maximum heap size reserved for the JVM (defaults to 2g).
 
 By default, Elasticsearch will listen to the public interfaces (`_site_` cf. https://www.elastic.co/guide/en/elasticsearch/reference/5.0/important-settings.html#network.host), so you will have to secure it, with firewall rules for example.
diff --git a/elasticsearch/defaults/main.yml b/elasticsearch/defaults/main.yml
index 2a75b07a..c0d46bc9 100644
--- a/elasticsearch/defaults/main.yml
+++ b/elasticsearch/defaults/main.yml
@@ -4,3 +4,5 @@ elasticsearch_network_host: "[_site_, _local_]"
 elasticsearch_network_publish_host: "_site_"
 elasticsearch_custom_datadir: Null
 elasticsearch_custom_tmpdir: Null
+elasticsearch_jvm_xms: 2g
+elasticsearch_jvm_xmx: 2g
diff --git a/elasticsearch/tasks/bootstrap_checks.yml b/elasticsearch/tasks/bootstrap_checks.yml
index aff90d7e..f9f75e7a 100644
--- a/elasticsearch/tasks/bootstrap_checks.yml
+++ b/elasticsearch/tasks/bootstrap_checks.yml
@@ -26,6 +26,11 @@
   tags:
     - config
 
+- name: Create a system config directory for systemd overrides
+  file:
+    path: /etc/systemd/system/elasticsearch.service.d
+    state: directory
+
 - name: Override memory config in systemd unit
   ini_file:
     dest: /etc/systemd/system/elasticsearch.service.d/elasticsearch.conf
diff --git a/elasticsearch/tasks/configuration.yml b/elasticsearch/tasks/configuration.yml
index 6d14f1a3..e51f434e 100644
--- a/elasticsearch/tasks/configuration.yml
+++ b/elasticsearch/tasks/configuration.yml
@@ -47,3 +47,19 @@
     insertafter: "^# *RESTART_ON_UPGRADE=true"
   tags:
     - config
+
+- name: JVM Heap size (min) is set
+  lineinfile:
+    dest: /etc/elasticsearch/jvm.options
+    regexp: "^-Xms"
+    line: "-Xms{{ elasticsearch_jvm_xms }}"
+  tags:
+    - config
+
+- name: JVM Heap size (max) is set
+  lineinfile:
+    dest: /etc/elasticsearch/jvm.options
+    regexp: "^-Xmx"
+    line: "-Xmx{{ elasticsearch_jvm_xmx }}"
+  tags:
+    - config
diff --git a/logstash/README.md b/logstash/README.md
index e4b16a34..3bad5cde 100644
--- a/logstash/README.md
+++ b/logstash/README.md
@@ -6,5 +6,10 @@ Install Logstash.
 
 Everything is in the `tasks/main.yml` file.
 
+## Variables
+
+* `logstash_jvm_xms`: minimum heap size reserved for the JVM (defaults to 256m).
+* `logstash_jvm_xmx`: maximum heap size reserved for the JVM (defaults to 1g).
+
 The pipeline must be configured before starting Logstash.
 https://www.elastic.co/guide/en/logstash/5.0/index.html
diff --git a/logstash/defaults/main.yml b/logstash/defaults/main.yml
new file mode 100644
index 00000000..e853af53
--- /dev/null
+++ b/logstash/defaults/main.yml
@@ -0,0 +1,2 @@
+logstash_jvm_xms: 256m
+logstash_jvm_xmx: 1g
diff --git a/logstash/tasks/main.yml b/logstash/tasks/main.yml
index 1a321e5b..58e3c006 100644
--- a/logstash/tasks/main.yml
+++ b/logstash/tasks/main.yml
@@ -12,3 +12,20 @@
   service:
     name: logstash
     enabled: yes
+
+
+- name: JVM Heap size (min) is set
+  lineinfile:
+    dest: /etc/logstash/jvm.options
+    regexp: "^-Xms"
+    line: "-Xms{{ logstash_jvm_xms }}"
+  tags:
+    - config
+
+- name: JVM Heap size (max) is set
+  lineinfile:
+    dest: /etc/logstash/jvm.options
+    regexp: "^-Xmx"
+    line: "-Xmx{{ logstash_jvm_xmx }}"
+  tags:
+    - config