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8306929: Avoid CleanClassLoaderDataMetaspaces safepoints when previous versions are shared

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Reviewed-by: coleenp, sspitsyn
This commit is contained in:
Stefan Johansson 2023-05-04 11:00:44 +00:00
parent cecf817f5e
commit 408cec516b
6 changed files with 147 additions and 23 deletions
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2
src/hotspot/share/classfile/classLoaderDataGraph.cpp
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@ -194,7 +194,7 @@ void ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces() {
// on the stack or in the code cache, so we only have to repeat the full walk if
// they were found at that time.
// TODO: have redefinition clean old methods out of the code cache. They still exist in some places.
bool walk_all_metadata = InstanceKlass::has_previous_versions_and_reset();
bool walk_all_metadata = InstanceKlass::should_clean_previous_versions_and_reset();
MetadataOnStackMark md_on_stack(walk_all_metadata, /*redefinition_walk*/false);
clean_deallocate_lists(walk_all_metadata);

2
src/hotspot/share/classfile/classLoaderDataGraph.inline.hpp
View file

@ -73,7 +73,7 @@ bool ClassLoaderDataGraph::should_clean_metaspaces_and_reset() {
// Only clean metaspaces after full GC.
bool do_cleaning = _safepoint_cleanup_needed;
#if INCLUDE_JVMTI
do_cleaning = do_cleaning && (_should_clean_deallocate_lists || InstanceKlass::has_previous_versions());
do_cleaning = do_cleaning && (_should_clean_deallocate_lists || InstanceKlass::should_clean_previous_versions());
#else
do_cleaning = do_cleaning && _should_clean_deallocate_lists;
#endif

35
src/hotspot/share/oops/instanceKlass.cpp
View file

@ -4022,18 +4022,18 @@ void InstanceKlass::set_init_state(ClassState state) {
// Globally, there is at least one previous version of a class to walk
// during class unloading, which is saved because old methods in the class
// are still running. Otherwise the previous version list is cleaned up.
bool InstanceKlass::_has_previous_versions = false;
bool InstanceKlass::_should_clean_previous_versions = false;
// Returns true if there are previous versions of a class for class
// unloading only. Also resets the flag to false. purge_previous_version
// will set the flag to true if there are any left, i.e., if there's any
// work to do for next time. This is to avoid the expensive code cache
// walk in CLDG::clean_deallocate_lists().
bool InstanceKlass::has_previous_versions_and_reset() {
bool ret = _has_previous_versions;
log_trace(redefine, class, iklass, purge)("Class unloading: has_previous_versions = %s",
bool InstanceKlass::should_clean_previous_versions_and_reset() {
bool ret = _should_clean_previous_versions;
log_trace(redefine, class, iklass, purge)("Class unloading: should_clean_previous_versions = %s",
ret ? "true" : "false");
_has_previous_versions = false;
_should_clean_previous_versions = false;
return ret;
}
@ -4090,12 +4090,17 @@ void InstanceKlass::purge_previous_version_list() {
version++;
continue;
} else {
log_trace(redefine, class, iklass, purge)("previous version " PTR_FORMAT " is alive", p2i(pv_node));
assert(pvcp->pool_holder() != nullptr, "Constant pool with no holder");
guarantee (!loader_data->is_unloading(), "unloaded classes can't be on the stack");
live_count++;
// found a previous version for next time we do class unloading
_has_previous_versions = true;
if (pvcp->is_shared()) {
// Shared previous versions can never be removed so no cleaning is needed.
log_trace(redefine, class, iklass, purge)("previous version " PTR_FORMAT " is shared", p2i(pv_node));
} else {
// Previous version alive, set that clean is needed for next time.
_should_clean_previous_versions = true;
log_trace(redefine, class, iklass, purge)("previous version " PTR_FORMAT " is alive", p2i(pv_node));
}
}
// next previous version
@ -4195,13 +4200,19 @@ void InstanceKlass::add_previous_version(InstanceKlass* scratch_class,
return;
}
// Add previous version if any methods are still running.
// Set has_previous_version flag for processing during class unloading.
_has_previous_versions = true;
log_trace(redefine, class, iklass, add) ("scratch class added; one of its methods is on_stack.");
// Add previous version if any methods are still running or if this is
// a shared class which should never be removed.
assert(scratch_class->previous_versions() == nullptr, "shouldn't have a previous version");
scratch_class->link_previous_versions(previous_versions());
link_previous_versions(scratch_class);
if (cp_ref->is_shared()) {
log_trace(redefine, class, iklass, add) ("scratch class added; class is shared");
} else {
// We only set clean_previous_versions flag for processing during class
// unloading for non-shared classes.
_should_clean_previous_versions = true;
log_trace(redefine, class, iklass, add) ("scratch class added; one of its methods is on_stack.");
}
} // end add_previous_version()
#endif // INCLUDE_JVMTI

8
src/hotspot/share/oops/instanceKlass.hpp
View file

@ -715,7 +715,7 @@ public:
}
private:
static bool _has_previous_versions;
static bool _should_clean_previous_versions;
public:
static void purge_previous_versions(InstanceKlass* ik) {
if (ik->has_been_redefined()) {
@ -723,8 +723,8 @@ public:
}
}
static bool has_previous_versions_and_reset();
static bool has_previous_versions() { return _has_previous_versions; }
static bool should_clean_previous_versions_and_reset();
static bool should_clean_previous_versions() { return _should_clean_previous_versions; }
// JVMTI: Support for caching a class file before it is modified by an agent that can do retransformation
void set_cached_class_file(JvmtiCachedClassFileData *data) {
@ -744,7 +744,7 @@ public:
#else // INCLUDE_JVMTI
static void purge_previous_versions(InstanceKlass* ik) { return; };
static bool has_previous_versions_and_reset() { return false; }
static bool should_clean_previous_versions_and_reset() { return false; }
void set_cached_class_file(JvmtiCachedClassFileData *data) {
assert(data == nullptr, "unexpected call with JVMTI disabled");

10
test/hotspot/jtreg/serviceability/jvmti/RedefineClasses/RedefinePreviousVersions.java
View file

@ -24,7 +24,7 @@
/*
* @test
* @bug 8165246 8010319
* @summary Test has_previous_versions flag and processing during class unloading.
* @summary Test clean_previous_versions flag and processing during class unloading.
* @requires vm.jvmti
* @requires vm.opt.final.ClassUnloading
* @requires vm.flagless
@ -88,8 +88,8 @@ public class RedefinePreviousVersions {
"-Xlog:redefine+class+iklass+add=trace,redefine+class+iklass+purge=trace",
"RedefinePreviousVersions");
new OutputAnalyzer(pb.start())
.shouldContain("Class unloading: has_previous_versions = false")
.shouldContain("Class unloading: has_previous_versions = true")
.shouldContain("Class unloading: should_clean_previous_versions = false")
.shouldContain("Class unloading: should_clean_previous_versions = true")
.shouldHaveExitValue(0);
return;
}
@ -99,7 +99,7 @@ public class RedefinePreviousVersions {
// Redefine a class and create some garbage
// Since there are no methods running, the previous version is never added to the
// previous_version_list and the flag _has_previous_versions should stay false
// previous_version_list and the flag _should_clean_previous_versions should stay false
RedefineClassHelper.redefineClass(RedefinePreviousVersions_B.class, newB);
for (int i = 0; i < 10 ; i++) {
@ -119,7 +119,7 @@ public class RedefinePreviousVersions {
}
// Since a method of newRunning is running, this class should be added to the previous_version_list
// of Running, and _has_previous_versions should return true at class unloading.
// of Running, and _should_clean_previous_versions should return true at class unloading.
RedefineClassHelper.redefineClass(RedefinePreviousVersions_Running.class, newRunning);
for (int i = 0; i < 10 ; i++) {

113
test/hotspot/jtreg/serviceability/jvmti/RedefineClasses/RedefineSharedClassJFR.java Normal file
View file

@ -0,0 +1,113 @@
/*
* Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
* 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
* @bug 8306929
* @summary Verify clean_previous_versions when run with JFR and CDS
* @requires vm.jvmti
* @requires vm.cds
* @requires vm.hasJFR
* @requires vm.opt.final.ClassUnloading
* @requires vm.flagless
* @library /test/lib
* @run driver RedefineSharedClassJFR xshare-off
* @run driver RedefineSharedClassJFR xshare-on
*/
import java.util.ArrayList;
import java.util.List;
import jdk.test.lib.Platform;
import jdk.test.lib.process.ProcessTools;
import jdk.test.lib.process.OutputAnalyzer;
import jtreg.SkippedException;
public class RedefineSharedClassJFR {
private static final String SHOULD_CLEAN_TRUE = "Class unloading: should_clean_previous_versions = true";
private static final String SHOULD_CLEAN_FALSE = "Class unloading: should_clean_previous_versions = false";
private static final String SCRATCH_CLASS_ADDED_SHARED = "scratch class added; class is shared";
private static final String SCRATCH_CLASS_ADDED_ON_STACK = "scratch class added; one of its methods is on_stack.";
public static void main(String[] args) throws Exception {
// Skip test if default archive is supported.
if (!Platform.isDefaultCDSArchiveSupported()) {
throw new SkippedException("Supported platform");
}
// Test is run with JFR which will transform a number of classes. Depending
// on if the test is run with or without CDS the output will be different,
// due to the fact that shared classes can never be cleaned out after retranform.
if (args.length > 0) {
// When run with an argument the class is used as driver and should parse
// the output to verify it is correct given the command line.
List<String> baseCommand = List.of(
"-XX:StartFlightRecording",
"-Xlog:redefine+class+iklass+add=trace,redefine+class+iklass+purge=trace",
"RedefineSharedClassJFR");
if (args[0].equals("xshare-off")) {
// First case is with -Xshare:off. In this case no classes are shared
// and we should be able to clean out the retransformed classes. Verify
// that the cleaning is done when the GC is triggered.
List<String> offCommand = new ArrayList<>();
offCommand.add("-Xshare:off");
offCommand.addAll(baseCommand);
ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(offCommand);
new OutputAnalyzer(pb.start())
.shouldContain(SHOULD_CLEAN_TRUE)
.shouldNotContain(SHOULD_CLEAN_FALSE)
// We expect at least one of the transformed classes to be in use, if
// not the above check that should_clean_previous should be true will also
// fail. This check is to show what is expected.
.shouldContain(SCRATCH_CLASS_ADDED_ON_STACK)
.shouldNotContain(SCRATCH_CLASS_ADDED_SHARED)
.shouldHaveExitValue(0);
return;
} else if (args[0].equals("xshare-on")) {
// With -Xshare:on, the shared classes can never be cleaned out. Check the
// logs to verify we don't try to clean when we know it is not needed.
List<String> onCommand = new ArrayList<>();
onCommand.add("-Xshare:on");
onCommand.addAll(baseCommand);
ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(onCommand);
new OutputAnalyzer(pb.start())
.shouldContain(SHOULD_CLEAN_FALSE)
.shouldNotContain(SHOULD_CLEAN_TRUE)
.shouldContain(SCRATCH_CLASS_ADDED_SHARED)
// If the below line occurs, then should_clean_previous_versions will be
// true and the above shouldContain will trigger. This check is to
// show the intention that we don't expect any non-shared transformed
// classes to be in use.
.shouldNotContain(SCRATCH_CLASS_ADDED_ON_STACK)
.shouldHaveExitValue(0);
return;
}
}
// When run without any argument this class acts as test and we do a system GC
// to trigger cleaning and get the output we want to check.
System.gc();
}
}