RFR(L) 8231610 Relocate the CDS archive if it cannot be mapped to the requested address
coleen.phillimore at oracle.com
coleen.phillimore at oracle.com
Wed Nov 13 15:54:24 UTC 2019
I agree, the new diagnostic option looks good. Better than
SharedBaseAddress=0.
Thanks,
Coleen
On 11/13/19 10:37 AM, Jiangli Zhou wrote:
> Look good!
>
> Best,
> Jiangli
>
> On Tue, Nov 12, 2019 at 9:12 PM Ioi Lam <ioi.lam at oracle.com> wrote:
>>
>>
>> On 11/10/19 5:14 PM, Jiangli Zhou wrote:
>>
>>
>>
>> On Sun, Nov 10, 2019, 3:13 PM Ioi Lam <ioi.lam at oracle.com> wrote:
>>>
>>>
>>> On 11/9/19 8:25 PM, Jiangli Zhou wrote:
>>>> Hi Ioi,
>>>>
>>>> On Fri, Nov 8, 2019 at 1:35 PM Ioi Lam <ioi.lam at oracle.com> wrote:
>>>>> Hi Jiangli,
>>>>>
>>>>> Thanks for your comments. Please see my replies in-line:
>>>>>
>>>>> On 11/7/19 6:34 PM, Jiangli Zhou wrote:
>>>>>> On Thu, Nov 7, 2019 at 6:11 PM Jiangli Zhou <jianglizhou at google.com> wrote:
>>>>>>> I looked both 05.full and 06.delta webrevs. They look good.
>>>>>>>
>>>>>>> I still feel a bit uneasy about the potential runtime impact when data
>>>>>>> does get relocated. Long running apps/services may be shy away from
>>>>>>> enabling archive at runtime, if there is a detectable overhead even
>>>>>>> though it may only occur rarely. As relocation is enabled by default
>>>>>>> and users cannot turn it off, disabling with -Xshare:off entirely
>>>>>>> would become the only choice. Could you please create a new RFE
>>>>>>> (possibly with higher priority) to investigate the potential effect,
>>>>>>> or provide an option for users to opt-in relocation with the
>>>>>>> command-line switch?
>>>>> I created https://bugs.openjdk.java.net/browse/JDK-8233862
>>>>> Investigate performance benefit of relocating CDS archive to under 32G
>>>>>
>>>>> As I noted in the bug report, I ran benchmarks with CDS relocation
>>>>> on/off, and there's no sign of regression when the CDS archive is
>>>>> relocated. Please see the bug report for how to configure the VM to do
>>>>> the comparison.
>>>>>
>>>>> As you said before: "When enabling CDS we [google] noticed a small
>>>>> runtime overhead in JDK 11 recently with a benchmark. After I backported
>>>>> JDK-8213713 to 11, it seemed to reduce the runtime overhead that the
>>>>> benchmark was experiencing":
>>>>>
>>>>> Can you confirm whether this is stock JDK 11 or a special google build?
>>>>> Which test case did you use? Is it possible for you to run the tests
>>>>> again (using the exact before/after bits that you had when backporting
>>>>> JDK-8213713)? Can you check if narrow_klass_base and narrow_klass_shift
>>>>> are the same in your before/after builds?
>>>> Thanks for creating the RFE.
>>>>
>>>> JDK-8213713 closes the 1G gap between the shared space and class space
>>>> and everything else is unaffected. The compressed class base and shift
>>>> were the same for before and after applying JDK-8213713. The effect
>>>> was statistically observed for the benchmark since the difference was
>>>> very small and could be within noise level for single run comparison.
>>>> A small difference could still be important for some use cases so it
>>>> needs to be taken into consideration when designing and implementing
>>>> new changes.
>>> Hi Jiangli,
>>>
>>> Thanks for taking the time for doing the performance measurements.
>>>
>>> I also ran benchmarks in all 3 modes (no CDS, CDS without relocation,
>>> CDS with relocation), and did not see any significant performance with
>>> Octane-DeltaBlue, Octane-NavierStokes, SPECjbb2005-Tuned,
>>> JFR-SPECjbb2005-Tuned, SPECjvm2008-Serial-G1 and Tools-Javac-Hello.
>>>
>>>
>>>> A new command-line for archived metadata relocation may still be
>>>> valuable. It would also be helpful for debugging and diagnosis.
>>>>
>>> How about a diagnostic flag ArchiveRelocationMode:
>>>
>>> 0: (default) first map at preferred address, and if unsuccessful, map to
>>> alternative address;
>>> 1: always map to alternative address;
>>> 2: always map at preferred address, and if unsuccessful, do not map the
>>> archive;
>>>
>>> 1 is for testing relocation, as well as for easy performance measurement
>>> (replaces the use of -XX:SharedBaseAddress=0 in my current patch.).
>>> 2 is for avoiding potential regression that may be introduced by
>>> relocation (revert to JDK 13 behavior).
>>>
>>> What do you think? If you like this I'll open a CSR.
>>
>>
>> That sounds good to me!
>>
>>
>> Hi Jiangli,
>>
>> It turns out that CSR is not needed for adding a diagnostic flag.
>>
>> I implemented the flag as described above. See:
>>
>> http://cr.openjdk.java.net/~iklam/jdk14/8231610-relocate-cds-archive.v07-delta/
>>
>>
>> Thanks
>> - Ioi
>>
>>
>> Regards,
>> Jiangli
>>
>>> Thanks
>>> - Ioi
>>>
>>>
>>>
>>>>>> Forgot to say that when Java heap can fit into low 32G space, it takes
>>>>>> the class space size into account and leaves need space right above
>>>>>> (also in low 32G space) when reserving heap, for !UseSharedSpace. In
>>>>>> that case, it's more likely the class data and heap data can be
>>>>>> colocated successfully.
>>>>> The reason is not for "colocation". It's so that narrow_klass_base can
>>>>> be zero, and the klass pointer can be uncompressed with a shift (without
>>>>> also doing an addition).
>>>>>
>>>>> But with CDS enabled, we always hard code to use non-zero
>>>>> narrow_klass_base and 3 bit shift (for AOT). So by just relocating the
>>>>> CDS archive to under 32GB, without modifying how CDS handles
>>>>> narrow_klass_base/shift, I don't think we can expect any benefit.
>>>> I experimented with mapping the shared space in low 32G and placed
>>>> right above the Java heap. The class space was also allocated in the
>>>> low 32G space and after the mapped shared space in the experiment. The
>>>> compress class encoding was using 0 base and 3 shift, which was the
>>>> same as the encoding when CDS was disabled. I didn't observe runtime
>>>> performance difference when comparing that specific configuration with
>>>> the normal CDS mapping scheme (the shared space start at 32G and the
>>>> encoding is non-zero base and 3 shift).
>>>>
>>>> Thanks,
>>>> Jiangli
>>>>> For modern architectures, I am not aware of any inherent speed benefit
>>>>> simply by putting data (in our case much larger than a page) "close to
>>>>> each other" in the virtual address space. If you have any reference of
>>>>> that, please let me know.
>>>>>
>>>>> Thanks
>>>>> - Ioi
>>>>>
>>>>>> Thanks,
>>>>>> Jiangli
>>>>>>
>>>>>>> Regards,
>>>>>>> Jiangli
>>>>>>>
>>>>>>> On Thu, Nov 7, 2019 at 4:22 PM Ioi Lam <ioi.lam at oracle.com> wrote:
>>>>>>>> Hi Coleen,
>>>>>>>>
>>>>>>>> Thanks for the review. Here's an webrev that has incorporated your
>>>>>>>> suggestions:
>>>>>>>>
>>>>>>>> http://cr.openjdk.java.net/~iklam/jdk14/8231610-relocate-cds-archive.v06-delta/
>>>>>>>>
>>>>>>>> Please see comments in-line
>>>>>>>>
>>>>>>>> On 11/7/19 2:46 PM, coleen.phillimore at oracle.com wrote:
>>>>>>>>> Hi, I've done a more high level code review of this and it looks good!
>>>>>>>>>
>>>>>>>>> http://cr.openjdk.java.net/~iklam/jdk14/8231610-relocate-cds-archive.v05/src/hotspot/share/memory/archiveUtils.hpp.html
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I think these classes require comments on what they do and why. The
>>>>>>>>> comments you sent me offline look good.
>>>>>>>> I added more comments for ArchivePtrMarker::_compacted per your offline
>>>>>>>> request.
>>>>>>>>
>>>>>>>>> Also .hpp files shouldn't include .inline.hpp files, like
>>>>>>>>> bitMap.inline.hpp. Hopefully it's just a case of moving do_bit() into
>>>>>>>>> the cpp file.
>>>>>>>> I moved the do_bit() function into archiveUtils.inline.hpp, since is
>>>>>>>> used by 3 .cpp files, and performance is important.
>>>>>>>>
>>>>>>>>> I wonder if the exception list of classes to exclude should be a
>>>>>>>>> function in javaClasses.hpp/cpp where the explanation would make more
>>>>>>>>> sense? ie bool
>>>>>>>>> JavaClasses::has_injected_native_pointers(InstanceKlass* k);
>>>>>>>> I moved the checking code to javaClasses.cpp. Since we do (partially)
>>>>>>>> support java.lang.Class, which has injected native pointers, I named the
>>>>>>>> function as JavaClasses::is_supported_for_archiving instead. I also
>>>>>>>> massaged the comments a little for clarification.
>>>>>>>>
>>>>>>>>> Is there already an RFE to move the DumpSharedSpaces output from
>>>>>>>>> tty->print() to log_info() ?
>>>>>>>> I created https://bugs.openjdk.java.net/browse/JDK-8233826 (Change CDS
>>>>>>>> dumping tty->print_cr() to unified logging).
>>>>>>>>
>>>>>>>> Thanks
>>>>>>>> - Ioi
>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>> Coleen
>>>>>>>>>
>>>>>>>>> On 11/6/19 4:17 PM, Ioi Lam wrote:
>>>>>>>>>> Hi Jiangli,
>>>>>>>>>>
>>>>>>>>>> I've uploaded the webrev after integrating your comments:
>>>>>>>>>>
>>>>>>>>>> http://cr.openjdk.java.net/~iklam/jdk14/8231610-relocate-cds-archive.v05/
>>>>>>>>>>
>>>>>>>>>> http://cr.openjdk.java.net/~iklam/jdk14/8231610-relocate-cds-archive.v05-delta/
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Please see more replies below:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On 11/4/19 5:52 PM, Jiangli Zhou wrote:
>>>>>>>>>>> On Sun, Nov 3, 2019 at 10:27 PM Ioi Lam <ioi.lam at oracle.com
>>>>>>>>>>> <mailto:ioi.lam at oracle.com>> wrote:
>>>>>>>>>>>
>>>>>>>>>>> Hi Jiangli,
>>>>>>>>>>>
>>>>>>>>>>> Thank you so much for spending time reviewing this RFE!
>>>>>>>>>>>
>>>>>>>>>>> On 11/3/19 6:34 PM, Jiangli Zhou wrote:
>>>>>>>>>>> > Hi Ioi,
>>>>>>>>>>> >
>>>>>>>>>>> > Sorry for the delay again. Will try to put this on the top of my
>>>>>>>>>>> list
>>>>>>>>>>> > next week and reduce the turn-around time. The updates look
>>>>>>>>>>> good in
>>>>>>>>>>> > general.
>>>>>>>>>>> >
>>>>>>>>>>> > We might want to have a better strategy when choosing metadata
>>>>>>>>>>> > relocation address (when relocation is needed). Some
>>>>>>>>>>> > applications/benchmarks may be more sensitive to cache
>>>>>>>>>>> locality and
>>>>>>>>>>> > memory/data layout. There was a bug,
>>>>>>>>>>> > https://bugs.openjdk.java.net/browse/JDK-8213713 that caused
>>>>>>>>>>> 1G gap
>>>>>>>>>>> > between Java heap data and metadata before JDK 12. The gap
>>>>>>>>>>> seemed to
>>>>>>>>>>> > cause a small but noticeable runtime effect in one case that I
>>>>>>>>>>> came
>>>>>>>>>>> > across.
>>>>>>>>>>>
>>>>>>>>>>> I guess you're saying we should try to relocate the archive into
>>>>>>>>>>> somewhere under 32GB?
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> I don't yet have sufficient data that determins if mapping at low
>>>>>>>>>>> 32G produces better runtime performance. I experimented with that,
>>>>>>>>>>> but didn't see noticeable difference when comparing to mapping at
>>>>>>>>>>> the current default address. It doesn't hurt, I think. So it may be
>>>>>>>>>>> a better choice than relocating to a random address in high 32G
>>>>>>>>>>> space (when Java heap is in low 32G address space).
>>>>>>>>>> Maybe we should reconsider this when we have more concrete data for
>>>>>>>>>> the benefits of moving the compressed class space to under 32G.
>>>>>>>>>>
>>>>>>>>>> Please note that in metaspace.cpp, when CDS is disabled and the VM
>>>>>>>>>> fails to allocate the class space at the requested address
>>>>>>>>>> (0x7c000000 for 16GB heap), it also just allocates from a random
>>>>>>>>>> address (without trying to to search under 32GB):
>>>>>>>>>>
>>>>>>>>>> http://hg.openjdk.java.net/jdk/jdk/annotate/e767fa6a1d45/src/hotspot/share/memory/metaspace.cpp#l1128
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> This code has been there since 2013 and we have not seen any issues.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> Could you elaborate more about the performance issue, especially
>>>>>>>>>>> about
>>>>>>>>>>> cache locality? I looked at JDK-8213713 but it didn't mention about
>>>>>>>>>>> performance.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> When enabling CDS we noticed a small runtime overhead in JDK 11
>>>>>>>>>>> recently with a benchmark. After I backported JDK-8213713 to 11, it
>>>>>>>>>>> seemed to reduce the runtime overhead that the benchmark was
>>>>>>>>>>> experiencing.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Also, by default, we have non-zero narrow_klass_base and
>>>>>>>>>>> narrow_klass_shift = 3, and archive relocation doesn't change that:
>>>>>>>>>>>
>>>>>>>>>>> $ java -Xlog:cds=debug -version
>>>>>>>>>>> ... narrow_klass_base = 0x0000000800000000, narrow_klass_shift = 3
>>>>>>>>>>> $ java -Xlog:cds=debug -XX:SharedBaseAddress=0 -version
>>>>>>>>>>> ... narrow_klass_base = 0x00007f1e8b499000, narrow_klass_shift = 3
>>>>>>>>>>>
>>>>>>>>>>> We always use narrow_klass_shift due to this:
>>>>>>>>>>>
>>>>>>>>>>> // CDS uses LogKlassAlignmentInBytes for narrow_klass_shift. See
>>>>>>>>>>> //
>>>>>>>>>>> MetaspaceShared::initialize_dumptime_shared_and_meta_spaces() for
>>>>>>>>>>> // how dump time narrow_klass_shift is set. Although, CDS can
>>>>>>>>>>> work
>>>>>>>>>>> // with zero-shift mode also, to be consistent with AOT it uses
>>>>>>>>>>> // LogKlassAlignmentInBytes for klass shift so archived java
>>>>>>>>>>> heap objects
>>>>>>>>>>> // can be used at same time as AOT code.
>>>>>>>>>>> if (!UseSharedSpaces
>>>>>>>>>>> && (uint64_t)(higher_address - lower_base) <=
>>>>>>>>>>> UnscaledClassSpaceMax) {
>>>>>>>>>>> CompressedKlassPointers::set_shift(0);
>>>>>>>>>>> } else {
>>>>>>>>>>> CompressedKlassPointers::set_shift(LogKlassAlignmentInBytes);
>>>>>>>>>>> }
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Right. If we relocate to low 32G space, it needs to make sure that
>>>>>>>>>>> the range containing the mapped class data and class space must be
>>>>>>>>>>> encodable.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> > Here are some additional comments (minor).
>>>>>>>>>>> >
>>>>>>>>>>> > Could you please fix the long lines in the following?
>>>>>>>>>>> >
>>>>>>>>>>> > 1237 void
>>>>>>>>>>> java_lang_Class::update_archived_primitive_mirror_native_pointers(oop
>>>>>>>>>>> > archived_mirror) {
>>>>>>>>>>> > 1238 if (MetaspaceShared::relocation_delta() != 0) {
>>>>>>>>>>> > 1239 assert(archived_mirror->metadata_field(_klass_offset) ==
>>>>>>>>>>> > NULL, "must be for primitive class");
>>>>>>>>>>> > 1240
>>>>>>>>>>> > 1241 Klass* ak =
>>>>>>>>>>> > ((Klass*)archived_mirror->metadata_field(_array_klass_offset));
>>>>>>>>>>> > 1242 if (ak != NULL) {
>>>>>>>>>>> > 1243 archived_mirror->metadata_field_put(_array_klass_offset,
>>>>>>>>>>> > (Klass*)(address(ak) + MetaspaceShared::relocation_delta()));
>>>>>>>>>>> > 1244 }
>>>>>>>>>>> > 1245 }
>>>>>>>>>>> > 1246 }
>>>>>>>>>>> >
>>>>>>>>>>> > src/hotspot/share/memory/dynamicArchive.cpp
>>>>>>>>>>> >
>>>>>>>>>>> > 889 Thread* THREAD = Thread::current();
>>>>>>>>>>> > 890 Method::sort_methods(ik->methods(), /*set_idnums=*/true,
>>>>>>>>>>> > dynamic_dump_method_comparator);
>>>>>>>>>>> > 891 if (ik->default_methods() != NULL) {
>>>>>>>>>>> > 892 Method::sort_methods(ik->default_methods(),
>>>>>>>>>>> > /*set_idnums=*/false, dynamic_dump_method_comparator);
>>>>>>>>>>> > 893 }
>>>>>>>>>>> >
>>>>>>>>>>>
>>>>>>>>>>> OK will do.
>>>>>>>>>>>
>>>>>>>>>>> > Please see inlined comments below.
>>>>>>>>>>> >
>>>>>>>>>>> > On Mon, Oct 28, 2019 at 9:05 PM Ioi Lam <ioi.lam at oracle.com
>>>>>>>>>>> <mailto:ioi.lam at oracle.com>> wrote:
>>>>>>>>>>> >> Hi Jiangli,
>>>>>>>>>>> >>
>>>>>>>>>>> >> Thanks for the review. I've updated the patch according to your
>>>>>>>>>>> comments:
>>>>>>>>>>> >>
>>>>>>>>>>> >>
>>>>>>>>>>> http://cr.openjdk.java.net/~iklam/jdk14/8231610-relocate-cds-archive.v04/
>>>>>>>>>>>
>>>>>>>>>>> >>
>>>>>>>>>>> http://cr.openjdk.java.net/~iklam/jdk14/8231610-relocate-cds-archive.v04.delta/
>>>>>>>>>>>
>>>>>>>>>>> >>
>>>>>>>>>>> >> (the delta is on top of 8231610-relocate-cds-archive.v03.delta
>>>>>>>>>>> in my
>>>>>>>>>>> >> reply to Calvin's comments).
>>>>>>>>>>> >>
>>>>>>>>>>> >> On 10/27/19 9:13 PM, Jiangli Zhou wrote:
>>>>>>>>>>> >>> Hi Ioi,
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> Sorry for the delay. Here are my remaining comments.
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> - src/hotspot/share/memory/dynamicArchive.cpp
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 128 static intx _method_comparator_name_delta;
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> The name of the above variable is confusing. It's the value of
>>>>>>>>>>> >>> _buffer_to_target_delta. It's better to _buffer_to_target_delta
>>>>>>>>>>> >>> directly.
>>>>>>>>>>> >> _buffer_to_target_delta is a non-static field, but
>>>>>>>>>>> >> dynamic_dump_method_comparator() must be a static function so
>>>>>>>>>>> it can't
>>>>>>>>>>> >> use the non-static field easily.
>>>>>>>>>>> >
>>>>>>>>>>> > It sounds like an issue. _buffer_to_target_delta was made as a
>>>>>>>>>>> > non-static mostly because we might support more than one dynamic
>>>>>>>>>>> > archives in the future. However, today's usages bake in an
>>>>>>>>>>> assumption
>>>>>>>>>>> > that _buffer_to_target_delta is a singleton value. It is
>>>>>>>>>>> cleaner to
>>>>>>>>>>> > either make _buffer_to_target_delta as a static variable for
>>>>>>>>>>> now, or
>>>>>>>>>>> > adding an access API in DynamicArchiveBuilder to allow other
>>>>>>>>>>> code to
>>>>>>>>>>> > properly and correctly use the value.
>>>>>>>>>>>
>>>>>>>>>>> OK, I'll move it to a static variable.
>>>>>>>>>>>
>>>>>>>>>>> >
>>>>>>>>>>> >>> Also, we can do a quick pointer comparison of 'a_name' and
>>>>>>>>>>> >>> 'b_name' first before adjusting the pointers.
>>>>>>>>>>> >> I added this:
>>>>>>>>>>> >>
>>>>>>>>>>> >> if (a_name == b_name) {
>>>>>>>>>>> >> return 0;
>>>>>>>>>>> >> }
>>>>>>>>>>> >>
>>>>>>>>>>> >>> ---
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 934 void DynamicArchiveBuilder::relocate_buffer_to_target() {
>>>>>>>>>>> >>> ...
>>>>>>>>>>> >>> 944
>>>>>>>>>>> >>> 945 ArchivePtrMarker::compact(relocatable_base,
>>>>>>>>>>> relocatable_end);
>>>>>>>>>>> >>> ...
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 974 SharedDataRelocator patcher((address*)patch_base,
>>>>>>>>>>> >>> (address*)patch_end, valid_old_base, valid_old_end,
>>>>>>>>>>> >>> 975 valid_new_base, valid_new_end, addr_delta);
>>>>>>>>>>> >>> 976 ArchivePtrMarker::ptrmap()->iterate(&patcher);
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> Could we reduce the number of data re-iterations to help
>>>>>>>>>>> archive
>>>>>>>>>>> >>> dumping performance. The ArchivePtrMarker::compact operation
>>>>>>>>>>> can be
>>>>>>>>>>> >>> combined with the patching iteration.
>>>>>>>>>>> ArchivePtrMarker::compact API
>>>>>>>>>>> >>> can be removed.
>>>>>>>>>>> >> That's a good idea. I implemented it using a template parameter
>>>>>>>>>>> so that
>>>>>>>>>>> >> we can have max performance when relocating the archive at run
>>>>>>>>>>> time.
>>>>>>>>>>> >>
>>>>>>>>>>> >> I added comments to explain why the relocation is done here. The
>>>>>>>>>>> >> relocation is pretty rare (only when the base archive was not
>>>>>>>>>>> mapped at
>>>>>>>>>>> >> the default location).
>>>>>>>>>>> >>
>>>>>>>>>>> >>> ---
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 967 address valid_new_base =
>>>>>>>>>>> >>> (address)Arguments::default_SharedBaseAddress();
>>>>>>>>>>> >>> 968 address valid_new_end = valid_new_base +
>>>>>>>>>>> base_plus_top_size;
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> The debugging only code can be included under #ifdef ASSERT.
>>>>>>>>>>> >> These values are actually also used in debug logging so they
>>>>>>>>>>> can't be
>>>>>>>>>>> >> ifdef'ed out.
>>>>>>>>>>> >>
>>>>>>>>>>> >> Also, the c++ compiler is pretty good with eliding code
>>>>>>>>>>> that's no
>>>>>>>>>>> >> actually used. If I comment out all the logging code in
>>>>>>>>>>> >> DynamicArchiveBuilder::relocate_buffer_to_target() and
>>>>>>>>>>> >> SharedDataRelocator, gcc elides all the unused fields and their
>>>>>>>>>>> >> assignments. So no code is generated for this, etc.
>>>>>>>>>>> >>
>>>>>>>>>>> >> address valid_new_base =
>>>>>>>>>>> >> (address)Arguments::default_SharedBaseAddress();
>>>>>>>>>>> >>
>>>>>>>>>>> >> Since #ifdef ASSERT makes the code harder to read, I think we
>>>>>>>>>>> should use
>>>>>>>>>>> >> it only when really necessary.
>>>>>>>>>>> > It seems cleaner to get rid of these debugging only variables, by
>>>>>>>>>>> > using 'relocatable_base' and
>>>>>>>>>>> > '(address)Arguments::default_SharedBaseAddress()' in the logging
>>>>>>>>>>> code.
>>>>>>>>>>>
>>>>>>>>>>> SharedDataRelocator is used under 3 different situations. These six
>>>>>>>>>>> variables (patch_base, patch_end, valid_old_base, valid_old_end,
>>>>>>>>>>> valid_new_base, valid_new_end) describes what is being patched,
>>>>>>>>>>> and what
>>>>>>>>>>> the expectations are, for each situation. The code will be hard to
>>>>>>>>>>> understand without them.
>>>>>>>>>>>
>>>>>>>>>>> Please note there's also logging code in the SharedDataRelocator
>>>>>>>>>>> constructor that prints out these values.
>>>>>>>>>>>
>>>>>>>>>>> I think I'll just remove the 'debug only' comment to avoid
>>>>>>>>>>> confusion.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Ok.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> >
>>>>>>>>>>> >>> ---
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 993
>>>>>>>>>>> dynamic_info->write_bitmap_region(ArchivePtrMarker::ptrmap());
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> We could combine the archived heap data bitmap into the new
>>>>>>>>>>> region as
>>>>>>>>>>> >>> well? It can be handled as a separate RFE.
>>>>>>>>>>> >> I've filed https://bugs.openjdk.java.net/browse/JDK-8233093
>>>>>>>>>>> >>
>>>>>>>>>>> >>> - src/hotspot/share/memory/filemap.cpp
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 1038 if (is_static()) {
>>>>>>>>>>> >>> 1039 if (errno == ENOENT) {
>>>>>>>>>>> >>> 1040 // Not locating the shared archive is ok.
>>>>>>>>>>> >>> 1041 fail_continue("Specified shared archive not found
>>>>>>>>>>> (%s).",
>>>>>>>>>>> >>> _full_path);
>>>>>>>>>>> >>> 1042 } else {
>>>>>>>>>>> >>> 1043 fail_continue("Failed to open shared archive file
>>>>>>>>>>> (%s).",
>>>>>>>>>>> >>> 1044 os::strerror(errno));
>>>>>>>>>>> >>> 1045 }
>>>>>>>>>>> >>> 1046 } else {
>>>>>>>>>>> >>> 1047 log_warning(cds, dynamic)("specified dynamic archive
>>>>>>>>>>> >>> doesn't exist: %s", _full_path);
>>>>>>>>>>> >>> 1048 }
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> If the top layer is explicitly specified by the user, a
>>>>>>>>>>> warning does
>>>>>>>>>>> >>> not seem to be a proper behavior if the VM fails to open the
>>>>>>>>>>> archive
>>>>>>>>>>> >>> file.
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> If might be better to handle the relocation unrelated code in
>>>>>>>>>>> separate
>>>>>>>>>>> >>> changeset and track with a separate RFE.
>>>>>>>>>>> >> This code was moved from
>>>>>>>>>>> >>
>>>>>>>>>>> >>
>>>>>>>>>>> http://hg.openjdk.java.net/jdk/jdk/file/d3382812b788/src/hotspot/share/memory/dynamicArchive.cpp#l1070
>>>>>>>>>>>
>>>>>>>>>>> >>
>>>>>>>>>>> >> so I am not changing the behavior. If you want, we can file an
>>>>>>>>>>> REF to
>>>>>>>>>>> >> change the behavior.
>>>>>>>>>>> > Ok. A new RFE sounds like the right thing to re-evaluable the
>>>>>>>>>>> usage
>>>>>>>>>>> > issue here. Thanks.
>>>>>>>>>>>
>>>>>>>>>>> I created https://bugs.openjdk.java.net/browse/JDK-8233446
>>>>>>>>>>>
>>>>>>>>>>> >>> ---
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 1148 void FileMapInfo::write_region(int region, char* base,
>>>>>>>>>>> size_t size,
>>>>>>>>>>> >>> 1149 bool read_only, bool
>>>>>>>>>>> allow_exec) {
>>>>>>>>>>> >>> ...
>>>>>>>>>>> >>> 1154
>>>>>>>>>>> >>> 1155 if (region == MetaspaceShared::bm) {
>>>>>>>>>>> >>> 1156 target_base = NULL;
>>>>>>>>>>> >>> 1157 } else if (DynamicDumpSharedSpaces) {
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> It's not too clear to me how the bitmap (bm) region is handled
>>>>>>>>>>> for the
>>>>>>>>>>> >>> base layer and top layer. Could you please explain?
>>>>>>>>>>> >> The bm region for both layers are mapped at an address picked
>>>>>>>>>>> by the OS:
>>>>>>>>>>> >>
>>>>>>>>>>> >> char* FileMapInfo::map_relocation_bitmap(size_t& bitmap_size) {
>>>>>>>>>>> >> FileMapRegion* si = space_at(MetaspaceShared::bm);
>>>>>>>>>>> >> bitmap_size = si->used_aligned();
>>>>>>>>>>> >> bool read_only = true, allow_exec = false;
>>>>>>>>>>> >> char* requested_addr = NULL; // allow OS to pick any
>>>>>>>>>>> location
>>>>>>>>>>> >> char* bitmap_base = os::map_memory(_fd, _full_path,
>>>>>>>>>>> si->file_offset(),
>>>>>>>>>>> >> requested_addr, bitmap_size,
>>>>>>>>>>> >> read_only, allow_exec);
>>>>>>>>>>> >>
>>>>>>>>>>> > Ok, after staring at the code for a few seconds I saw that's
>>>>>>>>>>> intended.
>>>>>>>>>>> > If the current region is 'bm', then the 'target_base' is NULL
>>>>>>>>>>> > regardless if it's static or dynamic archive. Otherwise, the
>>>>>>>>>>> > 'target_base' is handled differently for the static and dynamic
>>>>>>>>>>> case.
>>>>>>>>>>> > The following would be cleaner and has better reliability.
>>>>>>>>>>> >
>>>>>>>>>>> > char* target_base = NULL;
>>>>>>>>>>> >
>>>>>>>>>>> > // The target_base is NULL for 'bm' region.
>>>>>>>>>>> > if (!region == MetaspaceShared::bm) {
>>>>>>>>>>> > if (DynamicDumpSharedSpaces) {
>>>>>>>>>>> > assert(!HeapShared::is_heap_region(region), "dynamic
>>>>>>>>>>> archive
>>>>>>>>>>> > doesn't support heap regions");
>>>>>>>>>>> > target_base = DynamicArchive::buffer_to_target(base);
>>>>>>>>>>> > } else {
>>>>>>>>>>> > target_base = base;
>>>>>>>>>>> > }
>>>>>>>>>>> > }
>>>>>>>>>>>
>>>>>>>>>>> How about this?
>>>>>>>>>>>
>>>>>>>>>>> char* target_base;
>>>>>>>>>>> if (region == MetaspaceShared::bm) {
>>>>>>>>>>> target_base = NULL; // always NULL for bm region.
>>>>>>>>>>> } else {
>>>>>>>>>>> if (DynamicDumpSharedSpaces) {
>>>>>>>>>>> assert(!HeapShared::is_heap_region(region), "dynamic
>>>>>>>>>>> archive
>>>>>>>>>>> doesn't support heap regions");
>>>>>>>>>>> target_base = DynamicArchive::buffer_to_target(base);
>>>>>>>>>>> } else {
>>>>>>>>>>> target_base = base;
>>>>>>>>>>> }
>>>>>>>>>>> }
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> No objection If you prefer the extra 'else' block.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> >
>>>>>>>>>>> >>> ---
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 1362
>>>>>>>>>>> DEBUG_ONLY(header()->set_mapped_base_address((char*)(uintptr_t)0xdeadbeef);)
>>>>>>>>>>>
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> Could you please explain the above?
>>>>>>>>>>> >> I added the comments
>>>>>>>>>>> >>
>>>>>>>>>>> >> // Make sure we don't attempt to use
>>>>>>>>>>> header()->mapped_base_address()
>>>>>>>>>>> >> unless
>>>>>>>>>>> >> // it's been successfully mapped.
>>>>>>>>>>> >>
>>>>>>>>>>> DEBUG_ONLY(header()->set_mapped_base_address((char*)(uintptr_t)0xdeadbeef);)
>>>>>>>>>>>
>>>>>>>>>>> >>
>>>>>>>>>>> >>> ---
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 1359 FileMapRegion* last_region = NULL;
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 1371 if (last_region != NULL) {
>>>>>>>>>>> >>> 1372 // Ensure that the OS won't be able to allocate new
>>>>>>>>>>> memory
>>>>>>>>>>> >>> spaces between any mapped
>>>>>>>>>>> >>> 1373 // regions, or else it would mess up the simple
>>>>>>>>>>> comparision
>>>>>>>>>>> >>> in MetaspaceObj::is_shared().
>>>>>>>>>>> >>> 1374 assert(si->mapped_base() ==
>>>>>>>>>>> last_region->mapped_end(),
>>>>>>>>>>> >>> "must have no gaps");
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 1379 last_region = si;
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> Can you please place 'last_region' related code under #ifdef
>>>>>>>>>>> ASSERT?
>>>>>>>>>>> >> I think that will make the code more cluttered. The compiler
>>>>>>>>>>> will
>>>>>>>>>>> >> optimize out that away.
>>>>>>>>>>> > It's cleaner to define debugging only variable for debugging only
>>>>>>>>>>> > builds. You can wrapper it and related usage with DEBUG_ONLY.
>>>>>>>>>>>
>>>>>>>>>>> OK, will do.
>>>>>>>>>>>
>>>>>>>>>>> >
>>>>>>>>>>> >>> ---
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 1478 char* FileMapInfo::map_relocation_bitmap(size_t&
>>>>>>>>>>> bitmap_size) {
>>>>>>>>>>> >>> 1479 FileMapRegion* si = space_at(MetaspaceShared::bm);
>>>>>>>>>>> >>> 1480 bitmap_size = si->used_aligned();
>>>>>>>>>>> >>> 1481 bool read_only = true, allow_exec = false;
>>>>>>>>>>> >>> 1482 char* requested_addr = NULL; // allow OS to pick any
>>>>>>>>>>> location
>>>>>>>>>>> >>> 1483 char* bitmap_base = os::map_memory(_fd, _full_path,
>>>>>>>>>>> si->file_offset(),
>>>>>>>>>>> >>> 1484 requested_addr, bitmap_size,
>>>>>>>>>>> >>> read_only, allow_exec);
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> We need to handle mapping failure here.
>>>>>>>>>>> >> It's handled here:
>>>>>>>>>>> >>
>>>>>>>>>>> >> bool FileMapInfo::relocate_pointers(intx addr_delta) {
>>>>>>>>>>> >> log_debug(cds, reloc)("runtime archive relocation start");
>>>>>>>>>>> >> size_t bitmap_size;
>>>>>>>>>>> >> char* bitmap_base = map_relocation_bitmap(bitmap_size);
>>>>>>>>>>> >> if (bitmap_base != NULL) {
>>>>>>>>>>> >> ...
>>>>>>>>>>> >> } else {
>>>>>>>>>>> >> log_error(cds)("failed to map relocation bitmap");
>>>>>>>>>>> >> return false;
>>>>>>>>>>> >> }
>>>>>>>>>>> >>
>>>>>>>>>>> > 'bitmap_base' is used immediately after map_memory(). So the
>>>>>>>>>>> check
>>>>>>>>>>> > needs to be done immediately after map_memory(), but not in the
>>>>>>>>>>> caller
>>>>>>>>>>> > of map_relocation_bitmap().
>>>>>>>>>>> >
>>>>>>>>>>> > 1490 char* bitmap_base = os::map_memory(_fd, _full_path,
>>>>>>>>>>> si->file_offset(),
>>>>>>>>>>> > 1491 requested_addr, bitmap_size,
>>>>>>>>>>> > read_only, allow_exec);
>>>>>>>>>>> > 1492
>>>>>>>>>>> > 1493 if (VerifySharedSpaces && bitmap_base != NULL &&
>>>>>>>>>>> > !region_crc_check(bitmap_base, bitmap_size, si->crc())) {
>>>>>>>>>>>
>>>>>>>>>>> OK, I'll fix that.
>>>>>>>>>>>
>>>>>>>>>>> >
>>>>>>>>>>> >
>>>>>>>>>>> >>> ---
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 1513 // debug only -- the current value of the pointers
>>>>>>>>>>> to be
>>>>>>>>>>> >>> patched must be within this
>>>>>>>>>>> >>> 1514 // range (i.e., must be between the requesed base
>>>>>>>>>>> address,
>>>>>>>>>>> >>> and the of the current archive).
>>>>>>>>>>> >>> 1515 // Note: top archive may point to objects in the base
>>>>>>>>>>> >>> archive, but not the other way around.
>>>>>>>>>>> >>> 1516 address valid_old_base =
>>>>>>>>>>> (address)header()->requested_base_address();
>>>>>>>>>>> >>> 1517 address valid_old_end = valid_old_base +
>>>>>>>>>>> mapping_end_offset();
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> Please place all FileMapInfo::relocate_pointers debugging only
>>>>>>>>>>> code
>>>>>>>>>>> >>> under #ifdef ASSERT.
>>>>>>>>>>> >> Ditto about ifdef ASSERT
>>>>>>>>>>> >>
>>>>>>>>>>> >>> - src/hotspot/share/memory/heapShared.cpp
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 441 void
>>>>>>>>>>> HeapShared::initialize_from_archived_subgraph(Klass* k) {
>>>>>>>>>>> >>> 442 if (!open_archive_heap_region_mapped() ||
>>>>>>>>>>> !MetaspaceObj::is_shared(k)) {
>>>>>>>>>>> >>> 443 return; // nothing to do
>>>>>>>>>>> >>> 444 }
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> When do we call HeapShared::initialize_from_archived_subgraph
>>>>>>>>>>> for a
>>>>>>>>>>> >>> klass that's not shared?
>>>>>>>>>>> >> I've removed the !MetaspaceObj::is_shared(k). I probably added
>>>>>>>>>>> that for
>>>>>>>>>>> >> debugging purposes only.
>>>>>>>>>>> >>
>>>>>>>>>>> >>> 616 DEBUG_ONLY({
>>>>>>>>>>> >>> 617 Klass* klass = orig_obj->klass();
>>>>>>>>>>> >>> 618 assert(klass !=
>>>>>>>>>>> SystemDictionary::Module_klass() &&
>>>>>>>>>>> >>> 619 klass !=
>>>>>>>>>>> SystemDictionary::ResolvedMethodName_klass() &&
>>>>>>>>>>> >>> 620 klass !=
>>>>>>>>>>> SystemDictionary::MemberName_klass() &&
>>>>>>>>>>> >>> 621 klass !=
>>>>>>>>>>> SystemDictionary::Context_klass() &&
>>>>>>>>>>> >>> 622 klass !=
>>>>>>>>>>> SystemDictionary::ClassLoader_klass(), "we
>>>>>>>>>>> >>> can only relocate metaspace object pointers inside
>>>>>>>>>>> java_lang_Class
>>>>>>>>>>> >>> instances");
>>>>>>>>>>> >>> 623 });
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> Let's leave the above for a separate RFE. I think assert is not
>>>>>>>>>>> >>> sufficient for the check. Also, why ResolvedMethodName,
>>>>>>>>>>> Module and
>>>>>>>>>>> >>> MemberName cannot be part of the graph?
>>>>>>>>>>> >>>
>>>>>>>>>>> >>>
>>>>>>>>>>> >> I added the following comment:
>>>>>>>>>>> >>
>>>>>>>>>>> >> DEBUG_ONLY({
>>>>>>>>>>> >> // The following are classes in
>>>>>>>>>>> share/classfile/javaClasses.cpp
>>>>>>>>>>> >> that have injected native pointers
>>>>>>>>>>> >> // to metaspace objects. To support these classes, we
>>>>>>>>>>> need to add
>>>>>>>>>>> >> relocation code similar to
>>>>>>>>>>> >> //
>>>>>>>>>>> java_lang_Class::update_archived_mirror_native_pointers.
>>>>>>>>>>> >> Klass* klass = orig_obj->klass();
>>>>>>>>>>> >> assert(klass != SystemDictionary::Module_klass() &&
>>>>>>>>>>> >> klass !=
>>>>>>>>>>> SystemDictionary::ResolvedMethodName_klass() &&
>>>>>>>>>>> >>
>>>>>>>>>>> > It's too restrictive to exclude those objects from the archived
>>>>>>>>>>> object
>>>>>>>>>>> > graph because metadata relocation, since metadata relocation is
>>>>>>>>>>> rare.
>>>>>>>>>>> > The trade-off doesn't seem to buy us much.
>>>>>>>>>>> >
>>>>>>>>>>> > Do you plan to add the needed relocation code?
>>>>>>>>>>>
>>>>>>>>>>> I looked more into this. Actually we cannot handle these 5
>>>>>>>>>>> classes at
>>>>>>>>>>> all, even without archive relocation:
>>>>>>>>>>>
>>>>>>>>>>> [1] #define MODULE_INJECTED_FIELDS(macro) \
>>>>>>>>>>> macro(java_lang_Module, module_entry, intptr_signature, false)
>>>>>>>>>>>
>>>>>>>>>>> -> module_entry is malloc'ed
>>>>>>>>>>>
>>>>>>>>>>> [2] #define RESOLVEDMETHOD_INJECTED_FIELDS(macro) \
>>>>>>>>>>> macro(java_lang_invoke_ResolvedMethodName, vmholder,
>>>>>>>>>>> object_signature, false) \
>>>>>>>>>>> macro(java_lang_invoke_ResolvedMethodName, vmtarget,
>>>>>>>>>>> intptr_signature, false)
>>>>>>>>>>>
>>>>>>>>>>> -> these fields are related to method handles and lambda forms,
>>>>>>>>>>> etc.
>>>>>>>>>>> They can't be easily be archived without implementing lambda form
>>>>>>>>>>> archiving. (I did a prototype; it's very complex and fragile).
>>>>>>>>>>>
>>>>>>>>>>> [3] #define CALLSITECONTEXT_INJECTED_FIELDS(macro) \
>>>>>>>>>>> macro(java_lang_invoke_MethodHandleNatives_CallSiteContext,
>>>>>>>>>>> vmdependencies, intptr_signature, false) \
>>>>>>>>>>> macro(java_lang_invoke_MethodHandleNatives_CallSiteContext,
>>>>>>>>>>> last_cleanup, long_signature, false)
>>>>>>>>>>>
>>>>>>>>>>> -> vmdependencies is malloc'ed.
>>>>>>>>>>>
>>>>>>>>>>> [4] #define
>>>>>>>>>>> MEMBERNAME_INJECTED_FIELDS(macro) \
>>>>>>>>>>> macro(java_lang_invoke_MemberName, vmindex, intptr_signature,
>>>>>>>>>>> false)
>>>>>>>>>>>
>>>>>>>>>>> -> this one is probably OK. Despite being declared as
>>>>>>>>>>> 'intptr_signature', it seems to be used just as an integer.
>>>>>>>>>>> However,
>>>>>>>>>>> MemberNames are typically used with [2] and [3]. So let's just
>>>>>>>>>>> forbid it
>>>>>>>>>>> to be safe.
>>>>>>>>>>>
>>>>>>>>>>> [2] [3] [4] are not used directly by regular Java code and are
>>>>>>>>>>> unlikely
>>>>>>>>>>> to be referenced (directly or indirectly) by static fields (except
>>>>>>>>>>> for
>>>>>>>>>>> the static fields in the classes in java.lang.invoke, which we
>>>>>>>>>>> probably
>>>>>>>>>>> won't support for heap archiving due to the problem I described for
>>>>>>>>>>> [2]). Objects of these types are typically referenced via constant
>>>>>>>>>>> pool
>>>>>>>>>>> entries.
>>>>>>>>>>>
>>>>>>>>>>> [5] #define CLASSLOADER_INJECTED_FIELDS(macro) \
>>>>>>>>>>> macro(java_lang_ClassLoader, loader_data, intptr_signature,
>>>>>>>>>>> false)
>>>>>>>>>>>
>>>>>>>>>>> -> loader_data is malloc'ed.
>>>>>>>>>>>
>>>>>>>>>>> So, I will change the DEBUG_ONLY into a product-mode check, and
>>>>>>>>>>> quit
>>>>>>>>>>> dumping if these objects are found in the object subgraph.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Sounds good. Can you please also add a comment with explanation.
>>>>>>>>>>>
>>>>>>>>>>> For ClassLoader and Module, it worth considering caching the
>>>>>>>>>>> additional native data some time in the future. Lois had suggested
>>>>>>>>>>> the Module part a while ago.
>>>>>>>>>> I think we can do that if/when we archive Modules directly into the
>>>>>>>>>> shared heap.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Maybe we should backport the check to older versions as well?
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> We should discuss with Andrew Haley for backports to JDK 11 update
>>>>>>>>>>> releases. Since the current OpenJDK 11 only applies Java heap
>>>>>>>>>>> archiving to a restricted set of JDK library code, I think it is
>>>>>>>>>>> safe without the new check.
>>>>>>>>>>>
>>>>>>>>>>> For non-LTS releases, it might not be worthwhile as they may not be
>>>>>>>>>>> widely used?
>>>>>>>>>> I agree. FYI, we (Oracle) have no plan for backporting more types of
>>>>>>>>>> heap object archiving, so the decision would be up to whoever that
>>>>>>>>>> decides to do so.
>>>>>>>>>>
>>>>>>>>>> Thanks
>>>>>>>>>> - Ioi
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> Thanks,
>>>>>>>>>>> Jiangli
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> >
>>>>>>>>>>> >>> - src/hotspot/share/memory/metaspace.cpp
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 1036 metaspace_rs =
>>>>>>>>>>> ReservedSpace(compressed_class_space_size(),
>>>>>>>>>>> >>> 1037 _reserve_alignment,
>>>>>>>>>>> >>> 1038 large_pages,
>>>>>>>>>>> >>> 1039 requested_addr);
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> Please fix indentation.
>>>>>>>>>>> >> Fixed.
>>>>>>>>>>> >>
>>>>>>>>>>> >>> - src/hotspot/share/memory/metaspaceClosure.hpp
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 78 enum SpecialRef {
>>>>>>>>>>> >>> 79 _method_entry_ref
>>>>>>>>>>> >>> 80 };
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> Are there other pointers that are not references to
>>>>>>>>>>> MetaspaceObj? If
>>>>>>>>>>> >>> _method_entry_ref is the only type, it's probably not worth
>>>>>>>>>>> defining
>>>>>>>>>>> >>> SpecialRef?
>>>>>>>>>>> >> There may be more types in the future, so I want to have a
>>>>>>>>>>> stable API
>>>>>>>>>>> >> that can be easily expanded without touching all the code that
>>>>>>>>>>> uses it.
>>>>>>>>>>> >>
>>>>>>>>>>> >>
>>>>>>>>>>> >>> - src/hotspot/share/memory/metaspaceShared.hpp
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 42 enum MapArchiveResult {
>>>>>>>>>>> >>> 43 MAP_ARCHIVE_SUCCESS,
>>>>>>>>>>> >>> 44 MAP_ARCHIVE_MMAP_FAILURE,
>>>>>>>>>>> >>> 45 MAP_ARCHIVE_OTHER_FAILURE
>>>>>>>>>>> >>> 46 };
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> If we want to define different failure types, it's probably
>>>>>>>>>>> worth
>>>>>>>>>>> >>> using separate types for relocation failure and validation
>>>>>>>>>>> failure.
>>>>>>>>>>> >> For now, I just need to distinguish between MMAP_FAILURE (where
>>>>>>>>>>> I should
>>>>>>>>>>> >> attempt to remap at an alternative address) and OTHER_FAILURE
>>>>>>>>>>> (where the
>>>>>>>>>>> >> CDS archive loading will fail -- due to validation error,
>>>>>>>>>>> insufficient
>>>>>>>>>>> >> memory, etc -- without attempting to remap.)
>>>>>>>>>>> >>
>>>>>>>>>>> >>> ---
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 193 static intx _mapping_delta; // FIXME rename
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> How about _relocation_delta?
>>>>>>>>>>> >> Changed as suggested.
>>>>>>>>>>> >>
>>>>>>>>>>> >>> - src/hotspot/share/oops/instanceKlass
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 1573 bool InstanceKlass::_disable_method_binary_search = false;
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> The use of _disable_method_binary_search is not necessary. You
>>>>>>>>>>> can use
>>>>>>>>>>> >>> DynamicDumpSharedSpaces for the purpose. That would make things
>>>>>>>>>>> >>> cleaner.
>>>>>>>>>>> >> If we always disable the binary search when
>>>>>>>>>>> DynamicDumpSharedSpaces is
>>>>>>>>>>> >> true, it will slow down normal execution of the Java program
>>>>>>>>>>> when
>>>>>>>>>>> >> -XX:ArchiveClassesAtExit has been specified, but the program
>>>>>>>>>>> hasn't exited.
>>>>>>>>>>> > Could you please add some comments to
>>>>>>>>>>> _disable_method_binary_search
>>>>>>>>>>> > with the above explanation? Thanks.
>>>>>>>>>>>
>>>>>>>>>>> OK
>>>>>>>>>>> >
>>>>>>>>>>> >>> - test/hotspot/jtreg/runtime/cds/SpaceUtilizationCheck.java
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 76 if (name.equals("s0") ||
>>>>>>>>>>> name.equals("s1")) {
>>>>>>>>>>> >>> 77 // String regions are listed at
>>>>>>>>>>> the end and
>>>>>>>>>>> >>> they may not be fully occupied.
>>>>>>>>>>> >>> 78 break;
>>>>>>>>>>> >>> 79 } else if (name.equals("bm")) {
>>>>>>>>>>> >>> 80 // Bitmap space does not have a
>>>>>>>>>>> requested address.
>>>>>>>>>>> >>> 81 break;
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> It's not part of your change, but could you please fix line 76
>>>>>>>>>>> - 78
>>>>>>>>>>> >>> since it is trivial. It seems the lines can be removed.
>>>>>>>>>>> >> Removed.
>>>>>>>>>>> >>
>>>>>>>>>>> >>> - /src/hotspot/share/memory/archiveUtils.hpp
>>>>>>>>>>> >>> The file name does not match with the macro '#ifndef
>>>>>>>>>>> >>> SHARE_MEMORY_SHAREDDATARELOCATOR_HPP'. Could you please rename
>>>>>>>>>>> >>> archiveUtils.* ? archiveRelocator.hpp and
>>>>>>>>>>> archiveRelocator.cpp are
>>>>>>>>>>> >>> more descriptive.
>>>>>>>>>>> >> I named the file archiveUtils.hpp so we can move other misc
>>>>>>>>>>> stuff used
>>>>>>>>>>> >> by dumping into this file (e.g., DumpRegion, WriteClosure from
>>>>>>>>>>> >> metaspaceShared.hpp), since theses are not used by the majority
>>>>>>>>>>> of the
>>>>>>>>>>> >> files that use metaspaceShared.hpp.
>>>>>>>>>>> >>
>>>>>>>>>>> >> I fixed the ifdef.
>>>>>>>>>>> >>
>>>>>>>>>>> >>> - src/hotspot/share/memory/archiveUtils.cpp
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> 36 void ArchivePtrMarker::initialize(CHeapBitMap* ptrmap,
>>>>>>>>>>> address*
>>>>>>>>>>> >>> ptr_base, address* ptr_end) {
>>>>>>>>>>> >>> 37 assert(_ptrmap == NULL, "initialize only once");
>>>>>>>>>>> >>> 38 _ptr_base = ptr_base;
>>>>>>>>>>> >>> 39 _ptr_end = ptr_end;
>>>>>>>>>>> >>> 40 _compacted = false;
>>>>>>>>>>> >>> 41 _ptrmap = ptrmap;
>>>>>>>>>>> >>> 42 _ptrmap->initialize(12 * M / sizeof(intptr_t)); //
>>>>>>>>>>> default
>>>>>>>>>>> >>> archive is about 12MB.
>>>>>>>>>>> >>> 43 }
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> Could we do a better estimate here? We could guesstimate the
>>>>>>>>>>> size
>>>>>>>>>>> >>> based on the current used class space and metaspace size. It's
>>>>>>>>>>> okay if
>>>>>>>>>>> >>> a larger bitmap used, since it can be reduced after all
>>>>>>>>>>> marking are
>>>>>>>>>>> >>> done.
>>>>>>>>>>> >> The bitmap is automatically expanded when necessary in
>>>>>>>>>>> >> ArchivePtrMarker::mark_pointer(). It's only about 1/32 or 1/64
>>>>>>>>>>> of the
>>>>>>>>>>> >> total archive size, so even if we do expand, the cost will be
>>>>>>>>>>> trivial.
>>>>>>>>>>> > The initial value is based on the default CDS archive. When
>>>>>>>>>>> dealing
>>>>>>>>>>> > with a really large archive, it would have to re-grow many times.
>>>>>>>>>>> > Also, using a hard-coded value is less desirable.
>>>>>>>>>>>
>>>>>>>>>>> OK, I changed it to the following
>>>>>>>>>>>
>>>>>>>>>>> // Use this as initial guesstimate. We should need less space
>>>>>>>>>>> in the
>>>>>>>>>>> // archive, but if we're wrong the bitmap will be expanded
>>>>>>>>>>> automatically.
>>>>>>>>>>> size_t estimated_archive_size =
>>>>>>>>>>> MetaspaceGC::capacity_until_GC();
>>>>>>>>>>> // But set it smaller in debug builds so we always test the
>>>>>>>>>>> expansion
>>>>>>>>>>> code.
>>>>>>>>>>> // (Default archive is about 12MB).
>>>>>>>>>>> DEBUG_ONLY(estimated_archive_size = 6 * M);
>>>>>>>>>>>
>>>>>>>>>>> // We need one bit per pointer in the archive.
>>>>>>>>>>> _ptrmap->initialize(estimated_archive_size / sizeof(intptr_t));
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Thanks!
>>>>>>>>>>> - Ioi
>>>>>>>>>>>
>>>>>>>>>>> >
>>>>>>>>>>> >>>
>>>>>>>>>>> >>>
>>>>>>>>>>> >>> On Wed, Oct 16, 2019 at 4:58 PM Jiangli Zhou
>>>>>>>>>>> <jianglizhou at google.com <mailto:jianglizhou at google.com>> wrote:
>>>>>>>>>>> >>>> Hi Ioi,
>>>>>>>>>>> >>>>
>>>>>>>>>>> >>>> This is another great step for CDS usability improvement.
>>>>>>>>>>> Thank you!
>>>>>>>>>>> >>>>
>>>>>>>>>>> >>>> I have a high level question (or request): could we consider
>>>>>>>>>>> >>>> separating the relocation work for 'direct' class metadata
>>>>>>>>>>> from other
>>>>>>>>>>> >>>> types of metadata (such as the shared system dictionary,
>>>>>>>>>>> symbol table,
>>>>>>>>>>> >>>> etc)? Initially we only relocate the tables and other
>>>>>>>>>>> archived global
>>>>>>>>>>> >>>> data. When each archived class is being loaded, we can
>>>>>>>>>>> relocate all
>>>>>>>>>>> >>>> the pointers within the current class. We could find the
>>>>>>>>>>> segment (for
>>>>>>>>>>> >>>> the current class) in the bitmap and update the pointers
>>>>>>>>>>> within the
>>>>>>>>>>> >>>> segment. That way we can reduce initial startup costs and
>>>>>>>>>>> also avoid
>>>>>>>>>>> >>>> relocating class data that's not used at runtime. In some
>>>>>>>>>>> real world
>>>>>>>>>>> >>>> large systems, an archive may contain extremely large
>>>>>>>>>>> number of
>>>>>>>>>>> >>>> classes.
>>>>>>>>>>> >>>>
>>>>>>>>>>> >>>> Following are partial review comments so we can move things
>>>>>>>>>>> forward.
>>>>>>>>>>> >>>> Still going through the rest of the changes.
>>>>>>>>>>> >>>>
>>>>>>>>>>> >>>> - src/hotspot/share/classfile/javaClasses.cpp
>>>>>>>>>>> >>>>
>>>>>>>>>>> >>>> 1218 void
>>>>>>>>>>> java_lang_Class::update_archived_mirror_native_pointers(oop
>>>>>>>>>>> >>>> archived_mirror) {
>>>>>>>>>>> >>>> 1219 Klass* k =
>>>>>>>>>>> ((Klass*)archived_mirror->metadata_field(_klass_offset));
>>>>>>>>>>> >>>> 1220 if (k != NULL) { // k is NULL for the primitive
>>>>>>>>>>> classes such as
>>>>>>>>>>> >>>> java.lang.Byte::TYPE <<<<<<<<<<<
>>>>>>>>>>> >>>> 1221 archived_mirror->metadata_field_put(_klass_offset,
>>>>>>>>>>> >>>> (Klass*)(address(k) + MetaspaceShared::mapping_delta()));
>>>>>>>>>>> >>>> 1222 }
>>>>>>>>>>> >>>> 1223 ...
>>>>>>>>>>> >>>>
>>>>>>>>>>> >>>> Primitive type mirrors are handled separately. Could you
>>>>>>>>>>> please verify
>>>>>>>>>>> >>>> if this call path happens for primitive type mirror?
>>>>>>>>>>> >>>>
>>>>>>>>>>> >>>> To answer my question above, looks like you added the
>>>>>>>>>>> following, which
>>>>>>>>>>> >>>> is to be used for primitive type mirrors. That seems to be
>>>>>>>>>>> the reason
>>>>>>>>>>> >>>> why update_archived_mirror_native_pointers is trying to also
>>>>>>>>>>> cover
>>>>>>>>>>> >>>> primitive type. It better to have a separate API for
>>>>>>>>>>> primitive type
>>>>>>>>>>> >>>> mirror, which is cleaner. And, we also can replace the above
>>>>>>>>>>> check at
>>>>>>>>>>> >>>> line 1220 to be an assert for regular mirrors.
>>>>>>>>>>> >>>>
>>>>>>>>>>> >>>> +void ReadClosure::do_mirror_oop(oop *p) {
>>>>>>>>>>> >>>> + do_oop(p);
>>>>>>>>>>> >>>> + oop mirror = *p;
>>>>>>>>>>> >>>> + if (mirror != NULL) {
>>>>>>>>>>> >>>> +
>>>>>>>>>>> java_lang_Class::update_archived_mirror_native_pointers(mirror);
>>>>>>>>>>> >>>> + }
>>>>>>>>>>> >>>> +}
>>>>>>>>>>> >>>> +
>>>>>>>>>>> >>>>
>>>>>>>>>>> >>>> How about renaming update_archived_mirror_native_pointers to
>>>>>>>>>>> >>>> update_archived_mirror_klass_pointers.
>>>>>>>>>>> >>>>
>>>>>>>>>>> >>>> It would be good to pass the current klass as an argument.
>>>>>>>>>>> We can
>>>>>>>>>>> >>>> verify the relocated pointer matches with the current klass
>>>>>>>>>>> pointer.
>>>>>>>>>>> >>>>
>>>>>>>>>>> >>>> We should also check if relocation is necessary before
>>>>>>>>>>> spending cycles
>>>>>>>>>>> >>>> to obtain the
>>
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