8269126: Rename G1AllowPreventiveGC option to G1UsePreventiveGC

Reviewed-by: kbarrett, iwalulya

Author: Thomas Schatzl

src/hotspot/share/gc/g1/g1Policy.cpp

@@ -1414,7 +1414,7 @@ static size_t get_num_regions_adjust_for_plab_waste(size_t byte_count) {
 }
 
 bool G1Policy::preventive_collection_required(uint alloc_region_count) {
-  if (!G1AllowPreventiveGC || !Universe::is_fully_initialized()) {
+  if (!G1UsePreventiveGC || !Universe::is_fully_initialized()) {
     // Don't attempt any preventive GC's if the feature is disabled,
     // or before initialization is complete.
     return false;

src/hotspot/share/gc/g1/g1_globals.hpp

@@ -309,7 +309,7 @@
           "disables this check.")                                           \
           range(0.0, (double)max_uintx)                                     \
                                                                             \
-  product(bool, G1AllowPreventiveGC, true, DIAGNOSTIC,                       \
+  product(bool, G1UsePreventiveGC, true, DIAGNOSTIC,                        \
           "Allows collections to be triggered proactively based on the      \
            number of free regions and the expected survival rates in each   \
            section of the heap.")

test/hotspot/jtreg/gc/g1/TestGCLogMessages.java

@@ -242,7 +242,7 @@ private void testWithEvacuationFailureLogs() throws Exception {
                                                                   "-XX:G1EvacuationFailureALotCount=100",
                                                                   "-XX:G1EvacuationFailureALotInterval=1",
                                                                   "-XX:+UnlockDiagnosticVMOptions",
-                                                                  "-XX:-G1AllowPreventiveGC",
+                                                                  "-XX:-G1UsePreventiveGC",
                                                                   "-Xlog:gc+phases=debug",
                                                                   GCTestWithEvacuationFailure.class.getName());
 
@@ -255,7 +255,7 @@ private void testWithEvacuationFailureLogs() throws Exception {
                                                    "-Xmn16M",
                                                    "-Xms32M",
                                                    "-XX:+UnlockDiagnosticVMOptions",
-                                                   "-XX:-G1AllowPreventiveGC",
+                                                   "-XX:-G1UsePreventiveGC",
                                                    "-Xlog:gc+phases=trace",
                                                    GCTestWithEvacuationFailure.class.getName());