diff --git a/src/etc/rc.subr.d/tmp b/src/etc/rc.subr.d/tmp
index 15a2caf75..a5daa5991 100755
--- a/src/etc/rc.subr.d/tmp
+++ b/src/etc/rc.subr.d/tmp
@@ -42,7 +42,15 @@ fi
 mkdir -p /tmp
 
 if [ ${USE_MFS_TMP} -ne 0 ]; then
-	mount -t tmpfs -o mode=01777 tmpfs /tmp
+	MAX_MFS_TMP=$(grep 'max_mfs_tmp' /conf/config.xml | sed 's/[^>]*>\([^<]*\)<.*/\1/')
+	MAX_MEM_SYS=$(sysctl -n hw.physmem)
+
+	if [ -z "${MAX_MFS_TMP}" ]; then
+		# cap to 50% by default to avoid swapping
+		MAX_MFS_TMP=50
+	fi
+
+	mount -t tmpfs -o mode=01777,size=$((MAX_MEM_SYS / 100 * MAX_MFS_TMP)) tmpfs /tmp
 else
 	rm -rf /tmp/*
 	chmod 1777 /tmp
diff --git a/src/www/system_advanced_misc.php b/src/www/system_advanced_misc.php
index 4b234a330..cd6118b74 100644
--- a/src/www/system_advanced_misc.php
+++ b/src/www/system_advanced_misc.php
@@ -77,7 +77,9 @@ if ($_SERVER['REQUEST_METHOD'] === 'GET') {
     $pconfig['crypto_hardware'] = !empty($config['system']['crypto_hardware']) ? explode(',', $config['system']['crypto_hardware']) : [];
     $pconfig['thermal_hardware'] = !empty($config['system']['thermal_hardware']) ? $config['system']['thermal_hardware'] : null;
     $pconfig['use_mfs_var'] = isset($config['system']['use_mfs_var']);
+    $pconfig['max_mfs_var'] = $config['system']['max_mfs_var'] ?? null;
     $pconfig['use_mfs_tmp'] = isset($config['system']['use_mfs_tmp']);
+    $pconfig['max_mfs_tmp'] = $config['system']['max_mfs_tmp'] ?? null;
     $pconfig['use_swap_file'] = isset($config['system']['use_swap_file']);
     $pconfig['dhparamusage'] = !empty($config['system']['dhparamusage']) ? $config['system']['dhparamusage'] : null;
     $pconfig['rrdbackup'] = !empty($config['system']['rrdbackup']) ? $config['system']['rrdbackup'] : null;
@@ -105,11 +107,27 @@ if ($_SERVER['REQUEST_METHOD'] === 'GET') {
     if (!empty($pconfig['crypto_hardware'])) {
         if (count(array_intersect($pconfig['crypto_hardware'], crypto_modules())) == count($pconfig['crypto_hardware'])) {
             $input_errors[] = gettext('Please select a valid Cryptographic Accelerator.');
-	}
+        }
     } else {
         $pconfig['crypto_hardware'] = [];
     }
 
+    if (isset($pconfig['max_mfs_var']) && $pconfig['max_mfs_var'] != '') {
+        if (!is_numeric($pconfig['max_mfs_var'])) {
+            $input_errors[] = gettext('Memory usage percentage is not a number.');
+        } else if ($pconfig['max_mfs_var'] < 0 || $pconfig['max_mfs_var'] > 100) {
+            $input_errors[] = gettext('Memory usage percentage out of bounds.');
+        }
+    }
+
+    if (isset($pconfig['max_mfs_tmp']) && $pconfig['max_mfs_tmp'] != '') {
+        if (!is_numeric($pconfig['max_mfs_tmp'])) {
+            $input_errors[] = gettext('Memory usage percentage is not a number.');
+        } else if ($pconfig['max_mfs_tmp'] < 0 || $pconfig['max_mfs_tmp'] > 100) {
+            $input_errors[] = gettext('Memory usage percentage out of bounds.');
+        }
+    }
+
     if (!empty($pconfig['thermal_hardware']) && !array_key_exists($pconfig['thermal_hardware'], thermal_modules())) {
         $input_errors[] = gettext("Please select a valid Thermal Hardware Sensor.");
     }
@@ -143,12 +161,26 @@ if ($_SERVER['REQUEST_METHOD'] === 'GET') {
             unset($config['system']['use_mfs_var']);
         }
 
+        if (isset($pconfig['max_mfs_var']) && $pconfig['max_mfs_var'] != '') {
+            $pconfig['max_mfs_var'] = trim($pconfig['max_mfs_var']);
+            $config['system']['max_mfs_var'] = $pconfig['max_mfs_var'];
+        } elseif (isset($config['system']['max_mfs_var'])) {
+            unset($config['system']['max_mfs_var']);
+        }
+
         if (!empty($pconfig['use_mfs_tmp'])) {
             $config['system']['use_mfs_tmp'] = true;
         } elseif (isset($config['system']['use_mfs_tmp'])) {
             unset($config['system']['use_mfs_tmp']);
         }
 
+        if (isset($pconfig['max_mfs_tmp']) && $pconfig['max_mfs_tmp'] != '') {
+            $pconfig['max_mfs_tmp'] = trim($pconfig['max_mfs_tmp']);
+            $config['system']['max_mfs_tmp'] = $pconfig['max_mfs_tmp'];
+        } elseif (isset($config['system']['max_mfs_tmp'])) {
+            unset($config['system']['max_mfs_tmp']);
+        }
+
         if (!empty($pconfig['use_swap_file'])) {
             /* set explicit value here in case we want to make it flexible */
             $config['system']['use_swap_file'] = 2048;
@@ -495,6 +527,15 @@ include("head.inc");
                   </div>
                 </td>
               </tr>
+              <tr>
+                <td><a id="help_for_max_mfs_var" href="#" class="showhelp"><i class="fa fa-info-circle"></i></a> <?=gettext('/var/log RAM usage'); ?></td>
+                <td>
+                  <input name="max_mfs_var" type="text" id="max_mfs_var" placeholder="50" value="<?= html_safe($pconfig['max_mfs_var']) ?>"/>
+                  <div class="hidden" data-for="help_for_max_mfs_var">
+                    <?= gettext('Percentage of RAM used for the respective memory disk. A value of "0" means unlimited.') ?>
+                  </div>
+                </td>
+              </tr>
               <tr>
                 <td><a id="help_for_use_mfs_tmp" href="#" class="showhelp"><i class="fa fa-info-circle"></i></a> <?=gettext('/tmp RAM disk'); ?></td>
                 <td>
@@ -505,6 +546,15 @@ include("head.inc");
                   </div>
                 </td>
               </tr>
+              <tr>
+                <td><a id="help_for_max_mfs_tmp" href="#" class="showhelp"><i class="fa fa-info-circle"></i></a> <?=gettext('/tmp RAM usage'); ?></td>
+                <td>
+                  <input name="max_mfs_tmp" type="text" id="max_mfs_tmp" placeholder="50" value="<?= html_safe($pconfig['max_mfs_tmp']) ?>"/>
+                  <div class="hidden" data-for="help_for_max_mfs_tmp">
+                    <?= gettext('Percentage of RAM used for the respective memory disk. A value of "0" means unlimited.') ?>
+                  </div>
+                </td>
+              </tr>
             </table>
           </div>
           <div class="content-box tab-content table-responsive __mb">