RFR: 8207812: Implement Dynamic CDS Archive
Jiangli Zhou
jianglizhou at google.com
Thu Apr 25 02:54:59 UTC 2019
Please see comments inlined.
On Tue, Apr 23, 2019 at 5:08 PM Calvin Cheung <calvin.cheung at oracle.com> wrote:
>
> Hi Jiangli,
>
> Thanks a lot for your review!
>
> On 4/22/19, 2:07 PM, Jiangli Zhou wrote:
> > Hi Calvin,
> >
> > Congrats on finalizing the dynamic archiving work and completing
> > testing. After the integration of the dynamic archiving, a follow-up
> > RFE can be done to merge the archiving/copying code in
> > dynamicArchive.* and metaspaceShared.* for better maintenance in the
> > future. As there are many duplicates between those two, having shared
> > implementation for both static and dynamic will be beneficial and
> > reduce the maintenance cost.
> I'll file an RFE for the above.
> >
> > Here are my comments mainly for additional cleanups and some minor issues.
> >
> > - src/hotspot/share/classfile/classLoader.cpp
> >
> > 1337 // FIXME: DynamicDumpSharedSpaces and --patch-modules are
> > mutually exclusive
> > 1338 assert(!DynamicDumpSharedSpaces, "sanity");
> >
> > I tagged the comment with 'FIXME' to serve as a reminder to add more
> > details. The reason DynamicDumpSharedSpaces is 'mutually exclusive'
> > with with --patch-modules because DynamicDumpSharedSpaces is only
> > enabled when UseSharedSpaces is also enabled. As --patch-modules is
> > not supported with UseSharedSpaces, it is not supported with
> > DynamicDumpSharedSpaces either.
> I've converted the FIXME to a comment.
> >
> > 1518 ik->set_shared_classpath_index(UNREGISTERED_INDEX);
> > 1519 SystemDictionaryShared::set_shared_class_misc_info(ik,
> > (ClassFileStream*)stream);
> >
> > Please add assert(DynamicDumpSharedSpaces, "sanity"); to the above
> > code. With the new dynamic archiving capability, it's now able to
> > load/archive a class with user defined classloader via this call path.
> > A comment explaining this is also needed.
> I tried the assert but it didn't work. Not only DynamicDumpSharedSpaces
> will go through that code path.
I should be more clear. The new code is only intended for the
DynamicDumpSharedSpaces, since the shared_classpath_index is set to
UNREGISTERED_INDEX by ClassLoaderExt::load_class when loading class
with "source:" in the class list file at static dumping time.
1518 ik->set_shared_classpath_index(UNREGISTERED_INDEX);
1519 SystemDictionaryShared::set_shared_class_misc_info(ik,
(ClassFileStream*)stream);
After thinking more, it's probably better to remove the following
marked code from ClassLoaderExt::load_class. That avoids setting twice
in two different places during static dumping. It also makes the code
cleaner.
InstanceKlass* ClassLoaderExt::load_class(Symbol* name, const char*
path, TRAPS) {
...
result->set_shared_classpath_index(UNREGISTERED_INDEX); <<<<<<<<<<<
SystemDictionaryShared::set_shared_class_misc_info(result, stream);
<<<<<<<<<<<<
> >
> > - src/hotspot/share/classfile/classLoaderExt.cpp
> >
> > 64 void ClassLoaderExt::setup_app_search_path() {
> > 65 assert(DumpSharedSpaces || DynamicDumpSharedSpaces,
> > 66 "this function is only used with -Xshare:dump");
> >
> > The above message needs to be updated to reflect the new command-line option.
> Done.
> >
> > 304 result->set_shared_classpath_index(UNREGISTERED_INDEX);
> > 305 SystemDictionaryShared::set_shared_class_misc_info(result,
> > stream);<<<<<<<<<<
> >
> > Why is the set_shared_class_misc_info call being removed? If this is a
> > bug fix for loading classes from the classlist for user defined
> > classloaders, it should be handled separately, and with a separate bug
> > ID as well.
> It is called in ClassLoader::record_result() from
> KlassFactory::create_from_stream().
Ok, this is related to the above comment.
> >
> > - src/hotspot/share/classfile/compactHashtable.cpp
> >
> > 207 size_t SimpleCompactHashtable::calculate_header_size() {
> > 208 // We have 5 fields. Each takes up sizeof(intptr_t). See
> > WriteClosure::do_u4
> > 209 size_t bytes = sizeof(intptr_t) * 5;
> > 210 return bytes;
> > 211 }
> >
> > 212
> > 213 void SimpleCompactHashtable::serialize_header(SerializeClosure* soc) {
> > 214 // NOTE: if you change this function, you MUST change the number 5 in
> > 215 // calculate_header_size() accordingly.
> > ...
> >
> > As a cleanup, a better way to handle this is to calculate the size
> > within SimpleCompactHashtable::serialize_header during serializing the
> > data and set the size value in a valuable.
> > SimpleCompactHashtable::calculate_header_size() should simply retrieve
> > the value. A renaming of
> > SimpleCompactHashtable::calculate_header_size() can also be done.
> I've checked with Ioi on this one. The problem is
> calculate_header_size() needs to be called during size estimation, and
> serialize_header is called after size estimation.
Can you please file a RFE for this? The current code is okay for the
first integration. It deserves some efforts to make it cleaner
(probably with a different solution) since it can be error-prone.
> >
> > - src/hotspot/share/classfile/dictionary.cpp
> >
> > 315 InstanceKlass* Dictionary::find_class(Symbol* name) {
> > 316 unsigned int hash = compute_hash(name);
> > 317 int index = hash_to_index(hash);
> > 318 return find_class(index, hash, name);
> > 319 }
> >
> > Looks like the new function is not references (unless I'm missing
> > something). Please remove the function.
> >
> > - src/hotspot/share/classfile/dictionary.hpp
> >
> > 65 InstanceKlass* find_class(Symbol* name);
> >
> > Same comment as the above.
> I've removed the function.
> >
> > - src/hotspot/share/classfile/symbolTable.cpp.
> >
> > 473 Symbol* const _archived; // used by UseSharedArchived2
> >
> > Please removed 'UseSharedArchived2'. The comment also needs more clarifications.
> >
> > I couldn't find any references to SymbolTableCreateEntry. Can you
> > please point to me where it is being used?
> I've removed the entire SymbolTableCreateEntry class. It was left there
> probably due to merge error.
> >
> > - src/hotspot/share/classfile/systemDictionaryShared.cpp
> >
> > 1218 if (DynamicDumpSharedSpaces) {
> > 1219 return false;
> > 1220 } else {
> >
> > The above case for DynamicDumpSharedSpaces needs to be examined
> > carefully. Can you please ask Harold (and Coleen or Karen) to take a
> > look? Also, a comment is needed to explain that we can complete all
> > verification checks at dynamic dumping time.
> I've added a comment. If it return false, the caller will call
> VerificationType::resolve_and_check_assignability().
> >
> > - src/hotspot/share/classfile/systemDictionaryShared.cpp
> >
> > 1279 ResourceMark rm;
> >
> > You can use 'ResourceMark rm(THREAD)'.
> Fixed.
> >
> > - src/hotspot/share/memory/allocation.hpp
> >
> > 255 //
> > 256 // When CDS is not enabled, both pointers are set to NULL.
> > 257 static void* _shared_metaspace_base; // (inclusive) low address
> > 258 static void* _shared_metaspace_top; // (exclusive) high addres
> >
> > Why the comment at line 256 was removed?
> I've added back the comment.
> >
> > - src/hotspot/share/memory/filemap.cpp
> >
> > 101 void FileMapInfo::fail_continue(const char *msg, ...) {
> > 102 va_list ap;
> > 103 va_start(ap, msg);
> > 104 if (_runtime_dynamic_info == NULL) {
> > 105 MetaspaceShared::set_archive_loading_failed();
> > 106 } else {
> > 107 DynamicArchive::disable();
> > 108 }
> >
> > The above fail_continue only works if _runtime_dynamic_info is setup
> > after the mapping the base archive. Comments should be add to explain
> > that.
> Comment added.
> >
> > Can you please rename '_runtime_dynamic_info' so it's more
> > descriptive? Maybe use 'dynamic_archive_info'.
> Renamed to '_dynamic_archive_info'.
> >
> > 587 bool FileMapInfo::same_files(const char* file1, const char* file2) {
> >
> > The usage of FileMapInfo::same_files is not necessary and should be
> > removed. The base archive's CRC checksum values are recorded in the
> > dynamic archive. The runtime verifies the CRC values to make sure the
> > same archive is used at dump time and runtime, regardless of the base
> > archive path or name. It is designed for all use cases:
> The same_files() function is also used in arguments.cpp:
> 3530 if (DynamicDumpSharedSpaces) {
> 3531 if (FileMapInfo::same_files(SharedArchiveFile,
> ArchiveClassesAtExit)) {
> 3532 vm_exit_during_initialization(
> 3533 "Cannot have the same archive file specified for
> -XX:SharedArchiveFile and -XX:ArchiveClassesAtExit",
> 3534 SharedArchiveFile);
> 3535 }
> 3536 }
>
> The function is also needed for the RFE:
> https://bugs.openjdk.java.net/browse/JDK-8211723
Ok. It should be treated a bug, not a RFE.
The shared path table check does not verify the path ordering (also
including the case when new path components are inserted). The bug
should be handled as a high priority task for dynamic archive.
>
> We still verify the CRC values during runtime.
> >
> > * base CDS archive is specified in the -XX:SharedArchiveFile at
> > dynamic dumping time
> > * -XX:SharedArchiveFile is not specified at dynamic dumping time,
> > default location for the default CDS archive is used
> > * default CDS archive is specified in the -XX:SharedArchiveFile at runtime
> > * default CDS archive is not specified in the -XX:SharedArchiveFile at
> > runtime, default location for the default CDS archive is used
> Regarding the fourth point above, the user could have a non-default base
> archive and only specify the top archive during runtime.
I would argue against it since it doesn't always work and adds extra
code. When the archive path/name is changed, the recorded one in the
dynamic archive would no longer work. User still need to specify the
path/name in the command-line. The use case only works for the default
CDS archive. For non-default CDS archive, specifying in the
command-line option results a cleaner design and less fragile code.
> >
> > In all above cases, the base archive CRC values check is sufficient.
> > The use of path/name is fragile and should be avoided. That will allow
> > you to remove the _base_archive_name_size from the dynamic archive.
> We still need the _base_archive_name_size and the base archive name in
> the header because of the above reason.
Please see my comment above.
> >
> > 752 if (is_static) {
> > 753 // FIXME check for dynamic header as well
> > 754 // FIXME Don't just check the last region -- check all regions!
> >
> > Can you please address the first FIXME at line 753?
> >
> > Checking the last region is sufficient since the archive is written is
> > sequential order. The second FIXME is not necessary.
> I've addressed the first FIXME and converted the second one to a comment.
> >
> > - src/hotspot/share/memory/metaspace.cpp
> >
> > 1417 bool Metaspace::contains(const void* ptr) {
> > 1418 // FIXME: need to check the dynamic archive
> >
> > Can you please remove the above FIXME? There is no need for a separate check.
> Done.
> >
> > - src/hotspot/share/memory/metaspaceShared.cpp
> >
> > 830 intptr_t* MetaspaceShared::fix_cpp_vtable_for_second_archive
> >
> > Can you please rename the function to fix_cpp_vtable_for_dynamic_archive?
> Done.
> >
> > - src/hotspot/share/oops/klass.cpp
> >
> > 527 assert (DumpSharedSpaces || DynamicDumpSharedSpaces,
> > 528 "only called for DumpSharedSpaces");
> >
> > 544 void Klass::remove_java_mirror() {
> > 545 assert(DumpSharedSpaces || DynamicDumpSharedSpaces, "only
> > called for DumpSharedSpaces");
> >
> > Please fix the messages above.
> Done.
> >
> > - src/hotspot/share/prims/whitebox.cpp
> >
> > 2332 {CC"getResolvedReferences",
> > CC"(Ljava/lang/Class;)Ljava/lang/Object;",
> > (void*)&WB_GetResolvedReferences},
> > 2333 {CC"linkClass", CC"(Ljava/lang/Class;)V",
> > (void*)&WB_LinkClass},
> > 2334 {CC"areOpenArchiveHeapObjectsMapped", CC"()Z",
> > (void*)&WB_AreOpenArchiveHeapObjectsMapped},
> >
> > Can you please align the indentation of line 2333 (to be the same as
> > line 2332 or 2334)?
> Aligned (void*) with line 2334. (It doesn't show in the webrev since
> only blank space changes)
> >
> > - src/hotspot/share/runtime/arguments.cpp
> >
> > 1491 bool Arguments::check_unsupported_cds_runtime_properties() {
> > 1492 assert(UseSharedSpaces, "this function is only used with
> > -Xshare:{on,auto}");
> > 1493 assert(ARRAY_SIZE(unsupported_properties) ==
> > ARRAY_SIZE(unsupported_options), "must be");
> > 1494 if (ArchiveClassesAtExit != NULL) {
> > 1495 // dynamic dumping, just return false,
> > check_unsupported_dumping_properties() will be called
> > 1496 // in init_shared_archive_paths().
> > 1497 return false;
> > 1498 }
> >
> > The check_unsupported_cds_runtime_properties() should be done for the
> > 'ArchiveClassesAtExit != NULL' case as well. Dynamic dumping is a
> > combination of both dump time and runtime.
> The 'ArchiveClassesAtExit != NULL' is for dumping CDS archive to the
> user's point of view, that's why the comments in lines 1495 and 1496.
> During runtime, ArchiveClassesAtExit will be NULL, so the
> check_unsupported_cds_runtime_properties() will be called as usual.
During dynamic dumping, UseSharedSpace is true. Dynamic dumping is
special case of the 'runtime', that's why Dynamic dumping it is a
combination of both dump time and runtime. So
check_unsupported_cds_runtime_properties() is also need for dynamic
dumping.
> >
> > 2729 // -Xshare:auto || -Xshare:dynamicDump
> >
> > As you've renamed the command-line argument for dynamic dumping
> > support, the comment needs to be fixed.
> Fixed.
> >
> > 3125 // Compiler threads may concurrently update the class
> > metadata (such as method entries), so it's
> > 3126 // unsafe with DumpSharedSpaces (which modifies the class
> > metadata in place). Let's disable
> > 3127 // compiler just to be safe.
> > 3128 //
> > 3129 // Note: this is not a concern for DynamicDumpSharedSpaces,
> > which makes a copy of the class metadata
> > 3130 // instead of modifying them in place. The copy is
> > inaccessible to the compiler.
> > 3131 set_mode_flags(_int);
> >
> > We need to come back to revisit the above for the 'static' archive
> > dumping at one point. There is a RFE filed for that, if I remember
> > correctly. Could you please add a 'TODO' notes in the above comment.
> Added TODO.
> >
> > A check should be done in arguments.cpp to make sure
> > DynamicDumpSharedSpaces is not manipulated from the command-line
> > directly. DynamicDumpSharedSpaces should not be enabled in the
> > command-line without ArchiveClassesAtExit being specified.
> Done.
> >
> > - src/hotspot/share/runtime/java.cpp
> >
> > 509
> > 510 // FIXME: is this the right place?
> > 511 if (DynamicDumpSharedSpaces) {
> > 512 DynamicArchive::dump();
> > 513 }
> >
> > Again, the above 'FIXME' is served as a cleanup reminder. Please get
> > opinions from others on this change. If the calling place is okay,
> > please remove the FIXME.
> Removed the FIXME for now. Checked with David H. He indicated there's no
> easy answer for this. Just need to do a lot of testing.
> > - test
> >
> > Could you please add a test case for setting DynamicDumpSharedSpaces
> > from command-line?
> Here's an incremental webrev which contains a new test:
>
> http://cr.openjdk.java.net/~ccheung/8207812_dynamic_cds_archive/delta_01_02/
>
> thanks,
> Calvin
> >
> > I only took a brief look of the test changes. Please ask Misha to
> > review the test changes as well.
> >
> > Thanks and regards,
> > Jiangli
Thanks,
Jiangli
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