SOLR-13492: perform explicit GC concurrently (#1370)

solr/CHANGES.txt

@@ -297,6 +297,9 @@ Other Changes
 
 * SOLR-14480: Fix or suppress warnings in solr/cloud/api (Erick Erickson)
 
+* SOLR-13492: Ensure explicit GCs are concurrent by adding '+ExplicitGCInvokesConcurrent'.
+  (Guna Sekhar Dora, Shawn Heisey, Munendra S N)
+
 ==================  8.5.2 ==================
 
 Consult the LUCENE_CHANGES.txt file for additional, low level, changes in this release.

solr/bin/solr

@@ -2152,7 +2152,8 @@ function start_solr() {
         '-XX:+ParallelRefProcEnabled' \
         '-XX:MaxGCPauseMillis=250' \
         '-XX:+UseLargePages' \
-        '-XX:+AlwaysPreTouch')
+        '-XX:+AlwaysPreTouch' \
+        '-XX:+ExplicitGCInvokesConcurrent')
   else
     GC_TUNE=($GC_TUNE)
   fi

solr/bin/solr.cmd

@@ -1212,7 +1212,8 @@ IF "%GC_TUNE%"=="" (
     -XX:+ParallelRefProcEnabled ^
     -XX:MaxGCPauseMillis=250 ^
     -XX:+UseLargePages ^
-    -XX:+AlwaysPreTouch
+    -XX:+AlwaysPreTouch ^
+    -XX:+ExplicitGCInvokesConcurrent
 )
 
 if !JAVA_MAJOR_VERSION! GEQ 9  (

solr/bin/solr.in.cmd

@@ -35,6 +35,7 @@ REM set GC_LOG_OPTS=-verbose:gc -XX:+PrintHeapAtGC -XX:+PrintGCDetails -XX:+Prin
 
 REM Various GC settings have shown to work well for a number of common Solr workloads.
 REM See solr.cmd GC_TUNE for the default list.
+REM set GC_TUNE=-XX:+ExplicitGCInvokesConcurrent
 REM set GC_TUNE=-XX:SurvivorRatio=4
 REM set GC_TUNE=%GC_TUNE% -XX:TargetSurvivorRatio=90
 REM set GC_TUNE=%GC_TUNE% -XX:MaxTenuringThreshold=8

solr/bin/solr.in.sh

@@ -47,6 +47,7 @@
 
 # These GC settings have shown to work well for a number of common Solr workloads
 #GC_TUNE=" \
+#-XX:+ExplicitGCInvokesConcurrent \
 #-XX:SurvivorRatio=4 \
 #-XX:TargetSurvivorRatio=90 \
 #-XX:MaxTenuringThreshold=8 \