--- old/src/share/vm/gc/g1/g1MarkSweep.cpp 2016-09-12 10:37:36.409117437 +0200 +++ new/src/share/vm/gc/g1/g1MarkSweep.cpp 2016-09-12 10:37:36.277112218 +0200 @@ -132,9 +132,16 @@ MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations); { G1RootProcessor root_processor(g1h, 1); - root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure, - &GenMarkSweep::follow_cld_closure, - &follow_code_closure); + if (ClassUnloading) { + root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure, + &GenMarkSweep::follow_cld_closure, + &follow_code_closure); + } else { + root_processor.process_all_roots_no_string_table( + &GenMarkSweep::follow_root_closure, + &GenMarkSweep::follow_cld_closure, + &follow_code_closure); + } } { @@ -157,7 +164,7 @@ // This is the point where the entire marking should have completed. assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed"); - { + if (ClassUnloading) { GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer()); // Unload classes and purge the SystemDictionary. --- old/src/share/vm/gc/g1/g1RootProcessor.cpp 2016-09-12 10:37:37.361155077 +0200 +++ new/src/share/vm/gc/g1/g1RootProcessor.cpp 2016-09-12 10:37:37.233150016 +0200 @@ -83,6 +83,7 @@ } process_vm_roots(closures, phase_times, worker_i); + process_string_table_roots(closures, phase_times, worker_i); { // Now the CM ref_processor roots. @@ -191,19 +192,34 @@ void G1RootProcessor::process_all_roots(OopClosure* oops, CLDClosure* clds, - CodeBlobClosure* blobs) { + CodeBlobClosure* blobs, + bool process_string_table) { AllRootsClosures closures(oops, clds); process_java_roots(&closures, NULL, 0); process_vm_roots(&closures, NULL, 0); - if (!_process_strong_tasks.is_task_claimed(G1RP_PS_CodeCache_oops_do)) { - CodeCache::blobs_do(blobs); + if (process_string_table) { + process_string_table_roots(&closures, NULL, 0); } + process_code_cache_roots(blobs, NULL, 0); _process_strong_tasks.all_tasks_completed(n_workers()); } +void G1RootProcessor::process_all_roots(OopClosure* oops, + CLDClosure* clds, + CodeBlobClosure* blobs) { + process_all_roots(oops, clds, blobs, true); +} + +void G1RootProcessor::process_all_roots_no_string_table(OopClosure* oops, + CLDClosure* clds, + CodeBlobClosure* blobs) { + assert(!ClassUnloading, "Should only be used when class unloading is disabled"); + process_all_roots(oops, clds, blobs, false); +} + void G1RootProcessor::process_java_roots(G1RootClosures* closures, G1GCPhaseTimes* phase_times, uint worker_i) { @@ -280,14 +296,23 @@ SystemDictionary::roots_oops_do(strong_roots, weak_roots); } } +} - { - G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::StringTableRoots, worker_i); - // All threads execute the following. A specific chunk of buckets - // from the StringTable are the individual tasks. - if (weak_roots != NULL) { - StringTable::possibly_parallel_oops_do(weak_roots); - } +void G1RootProcessor::process_string_table_roots(G1RootClosures* closures, + G1GCPhaseTimes* phase_times, + uint worker_i) { + assert(closures->weak_oops() != NULL, "Should only be called when all roots are processed"); + G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::StringTableRoots, worker_i); + // All threads execute the following. A specific chunk of buckets + // from the StringTable are the individual tasks. + StringTable::possibly_parallel_oops_do(closures->weak_oops()); +} + +void G1RootProcessor::process_code_cache_roots(CodeBlobClosure* code_closure, + G1GCPhaseTimes* phase_times, + uint worker_i) { + if (!_process_strong_tasks.is_task_claimed(G1RP_PS_CodeCache_oops_do)) { + CodeCache::blobs_do(code_closure); } } --- old/src/share/vm/gc/g1/g1RootProcessor.hpp 2016-09-12 10:37:38.141185916 +0200 +++ new/src/share/vm/gc/g1/g1RootProcessor.hpp 2016-09-12 10:37:38.025181330 +0200 @@ -73,6 +73,11 @@ void worker_has_discovered_all_strong_classes(); void wait_until_all_strong_classes_discovered(); + void process_all_roots(OopClosure* oops, + CLDClosure* clds, + CodeBlobClosure* blobs, + bool process_string_table); + void process_java_roots(G1RootClosures* closures, G1GCPhaseTimes* phase_times, uint worker_i); @@ -81,6 +86,14 @@ G1GCPhaseTimes* phase_times, uint worker_i); + void process_string_table_roots(G1RootClosures* closures, + G1GCPhaseTimes* phase_times, + uint worker_i); + + void process_code_cache_roots(CodeBlobClosure* code_closure, + G1GCPhaseTimes* phase_times, + uint worker_i); + public: G1RootProcessor(G1CollectedHeap* g1h, uint n_workers); @@ -99,6 +112,13 @@ CLDClosure* clds, CodeBlobClosure* blobs); + // Apply oops, clds and blobs to strongly and weakly reachable roots in the system, + // the only thing different from process_all_roots is that we skip the string table + // to avoid keeping every string live when doing class unloading. + void process_all_roots_no_string_table(OopClosure* oops, + CLDClosure* clds, + CodeBlobClosure* blobs); + // Number of worker threads used by the root processor. uint n_workers() const; }; --- old/src/share/vm/runtime/arguments.cpp 2016-09-12 10:37:39.213228301 +0200 +++ new/src/share/vm/runtime/arguments.cpp 2016-09-12 10:37:39.041221500 +0200 @@ -1687,11 +1687,6 @@ CompactibleFreeListSpaceLAB::modify_initialization(OldPLABSize, OldPLABWeight); } - if (!ClassUnloading) { - FLAG_SET_CMDLINE(bool, CMSClassUnloadingEnabled, false); - FLAG_SET_CMDLINE(bool, ExplicitGCInvokesConcurrentAndUnloadsClasses, false); - } - log_trace(gc)("MarkStackSize: %uk MarkStackSizeMax: %uk", (unsigned int) (MarkStackSize / K), (uint) (MarkStackSizeMax / K)); } #endif // INCLUDE_ALL_GCS @@ -2019,6 +2014,13 @@ // Keeping the heap 100% free is hard ;-) so limit it to 99%. FLAG_SET_ERGO(uintx, MinHeapFreeRatio, 99); } + + // If class unloading is disabled, also disable concurrent class unloading. + if (!ClassUnloading) { + FLAG_SET_CMDLINE(bool, CMSClassUnloadingEnabled, false); + FLAG_SET_CMDLINE(bool, ClassUnloadingWithConcurrentMark, false); + FLAG_SET_CMDLINE(bool, ExplicitGCInvokesConcurrentAndUnloadsClasses, false); + } #endif // INCLUDE_ALL_GCS } --- /dev/null 2016-09-05 16:43:01.836051253 +0200 +++ new/test/gc/class_unloading/TestClassUnloadingDisabled.java 2016-09-12 10:37:39.809251865 +0200 @@ -0,0 +1,118 @@ +/* + * Copyright (c) 2016, Oracle and/or its affiliates. All rights reqserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA + * or visit www.oracle.com if you need additional information or have any + * questions. + */ + +/* + * @test + * @key gc + * @bug 8114823 + * @requires vm.gc == null + * @requires vm.opt.ExplicitGCInvokesConcurrent != true + * @requires vm.opt.ClassUnloading != true + * @library /test/lib + * @modules java.base/jdk.internal.misc + * java.management + * @build sun.hotspot.WhiteBox + * @run main ClassFileInstaller sun.hotspot.WhiteBox + * sun.hotspot.WhiteBox$WhiteBoxPermission + * + * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI + * -XX:-ClassUnloading -XX:+UseG1GC TestClassUnloadingDisabled + * + * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI + * -XX:-ClassUnloading -XX:+UseSerialGC TestClassUnloadingDisabled + * + * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI + * -XX:-ClassUnloading -XX:+UseParallelGC TestClassUnloadingDisabled + * + * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI + * -XX:-ClassUnloading -XX:+UseConcMarkSweepGC TestClassUnloadingDisabled + */ + +import java.io.File; +import java.io.IOException; +import java.nio.file.Files; +import java.nio.file.Path; +import java.nio.file.Paths; + +import sun.hotspot.WhiteBox; + +import static jdk.test.lib.Asserts.*; + +public class TestClassUnloadingDisabled { + public static void main(String args[]) throws Exception { + final WhiteBox wb = WhiteBox.getWhiteBox(); + // Fetch the dir where the test class and the class + // to be loaded resides. + String classDir = TestClassUnloadingDisabled.class.getProtectionDomain().getCodeSource().getLocation().getPath(); + String className = "ClassToLoadUnload"; + + assertFalse(wb.isClassAlive(className), "Should not be loaded yet"); + + // The NoPDClassLoader handles loading classes in the test directory + // and loads them without a protection domain, which in some cases + // keeps the class live regardless of marking state. + NoPDClassLoader nopd = new NoPDClassLoader(classDir); + nopd.loadClass(className); + + assertTrue(wb.isClassAlive(className), "Class should be loaded"); + + // Clear the class-loader, class and object references to make + // class unloading possible. + nopd = null; + + System.gc(); + assertTrue(wb.isClassAlive(className), "Class should not have ben unloaded"); + } +} + +class NoPDClassLoader extends ClassLoader { + String path; + + NoPDClassLoader(String path) { + this.path = path; + } + + public Class loadClass(String name) throws ClassNotFoundException { + byte[] cls = null; + File f = new File(path,name + ".class"); + + // Delegate class loading if class not present in the given + // directory. + if (!f.exists()) { + return super.loadClass(name); + } + + try { + Path path = Paths.get(f.getAbsolutePath()); + cls = Files.readAllBytes(path); + } catch (IOException e) { + throw new ClassNotFoundException(name); + } + + // Define class with no protection domain and resolve it. + return defineClass(name, cls, 0, cls.length, null); + } +} + +class ClassToLoadUnload { +}