8277372: Add getters for BOT and card table members #6570

vish-chan · 2021-11-26T07:33:44Z

Changed the visibility, added getters and refactored the following:

Card Table Members
BOT members
ObjectStartArray block members

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Issue

JDK-8277372: Add getters for BOT and card table members

Reviewers

Thomas Schatzl (@tschatzl - Reviewer)
Stefan Johansson (@kstefanj - Reviewer) ⚠️ Review applies to 0f63516
Albert Mingkun Yang (@albertnetymk - Reviewer) ⚠️ Review applies to 0f63516

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/6570/head:pull/6570
$ git checkout pull/6570

Update a local copy of the PR:
$ git checkout pull/6570
$ git pull https://git.openjdk.java.net/jdk pull/6570/head

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Checkout this PR locally:
$ git pr checkout 6570

View PR using the GUI difftool:
$ git pr show -t 6570

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Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/6570.diff

bridgekeeper · 2021-11-26T07:34:26Z

👋 Welcome back vish-chan! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2021-11-26T07:36:29Z

@vish-chan The following label will be automatically applied to this pull request:

hotspot

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

mlbridge · 2021-11-26T07:41:23Z

Webrevs

tschatzl · 2021-11-27T12:10:17Z

@tstuefe : can you check whether the s390 and ppc changes still compile? The changes look straightforward enough, but...

Thanks,
Thomas

tstuefe · 2021-11-27T14:26:52Z

@tschatzl We have s390 + ppcle builds now in GHAs thanks to Alexey, and they do look fine (https://github.com/openjdk/jdk/pull/6570/checks?check_run_id=4341321057). Seeing how simple the platform changes are, I think this is okay.

Cheers, Thomas

tschatzl

I will push it through our testing, particular the changes for the SA agent (in vmstructs_gc.hpp) are always good to double-check.

tschatzl · 2021-11-29T09:49:13Z

src/hotspot/share/gc/shared/blockOffsetTable.hpp

+private:
+  static uint _LogN;
+  static uint _LogN_words;
+  static uint _N_bytes;
+  static uint _N_words;


The private visibility modifier can be removed as this is default at the top of a class.
The static variables should start with a lower case letter after the underscore, something like _log_n.

My suggestion would also be to change N/n to something more understandable, like size, and add block, i.e. something like _log_block_size, _log_block_size_in_words similar to the corresponding CardTable members etc.

Edit: note that "block" isn't a good word to use here, so scratch that - "block" is any kind of area that is more generic than an object, but does not refer to the BOT entry.

As I can understand, we need to replace "N" with something meaningful. Does something like "entry_size" or "bot_entry_size" would work?

I would think that bot_entry_size is one byte. Probably "bot_card_size"?

tschatzl

Getting good :) Some minor comments.

tschatzl · 2021-11-30T16:13:28Z

src/hotspot/share/gc/g1/g1BlockOffsetTable.cpp

@@ -287,12 +287,12 @@ void G1BlockOffsetTablePart::alloc_block_work(HeapWord** threshold_, HeapWord* b
  for (size_t j = orig_index + 1; j <= end_index; j++) {
    assert(_bot->offset_array(j) > 0 &&
           _bot->offset_array(j) <=
-             (u_char) (BOTConstants::N_words+BOTConstants::N_powers-1),
+             (u_char) (BOTConstants::bot_card_size_words()+BOTConstants::N_powers-1),


Suggested change

(u_char) (BOTConstants::bot_card_size_words()+BOTConstants::N_powers-1),

(u_char) (BOTConstants::bot_card_size_words() + BOTConstants::N_powers - 1),

Pre-existing: operator has no spaces around it

tschatzl · 2021-11-30T16:13:28Z

src/hotspot/share/gc/g1/g1BlockOffsetTable.cpp

           "offset array should have been set - "
           "%u not > 0 OR %u not <= %u",
           (uint) _bot->offset_array(j),
           (uint) _bot->offset_array(j),
-           (uint) (BOTConstants::N_words+BOTConstants::N_powers-1));
+           (uint) (BOTConstants::bot_card_size_words()+BOTConstants::N_powers-1));


Suggested change

(uint) (BOTConstants::bot_card_size_words()+BOTConstants::N_powers-1));

(uint) (BOTConstants::bot_card_size_words() + BOTConstants::N_powers - 1));

Pre-existing: spaces around operator

tschatzl · 2021-11-30T16:13:28Z

src/hotspot/share/gc/shared/cardTable.cpp

@@ -413,7 +413,7 @@ void CardTable::dirty_card_iterate(MemRegion mr, MemRegionClosure* cl) {
               next_entry <= limit && *next_entry == dirty_card;
               dirty_cards++, next_entry++);
          MemRegion cur_cards(addr_for(cur_entry),
-                              dirty_cards*card_size_in_words);
+                              dirty_cards*_card_size_in_words);


Suggested change

dirty_cards*_card_size_in_words);

dirty_cards * _card_size_in_words);

Pre-existing: spaces around operator

tschatzl · 2021-11-30T16:13:28Z

src/hotspot/share/gc/shared/cardTable.cpp

@@ -439,7 +439,7 @@ MemRegion CardTable::dirty_card_range_after_reset(MemRegion mr,
               next_entry <= limit && *next_entry == dirty_card;
               dirty_cards++, next_entry++);
          MemRegion cur_cards(addr_for(cur_entry),
-                              dirty_cards*card_size_in_words);
+                              dirty_cards*_card_size_in_words);


Suggested change

dirty_cards*_card_size_in_words);

dirty_cards * _card_size_in_words);

Pre-existing: spaces around operator

tschatzl · 2021-11-30T16:13:28Z

src/hotspot/share/gc/parallel/objectStartArray.hpp

+  static uint _block_shift;
+  static uint _block_size;
+  static uint _block_size_in_words;
+


Almost the same naming issue as in the BlockOffsetTable/SharedArray; I would prefer if these members (and getters) here were named similarly to the ones there.
It is true that ObjectStartArray and BlockOffsetTable are basically the same thing, but any eventual merge is another issue.

Shall these be renamed to osa_card_shift? Something like this?

Okay, _osa_card_shift and so on is also acceptable to me, but just _card_shift/_card_size would be fine too. We typically do not prefix members with abbreviations of class name they are in; I see now that we have that _bot prefix in the other class, for me the bot prefix not necessarily refers to the class but to the concept of a block offset table.

Maybe just reduce the names in both cases to _card_size/_card_shift/_log_card_<something>? What do others think?

You mean for both blockOffsetTable and objectStartArray, all the relevant members be renamed to _card_size and so on?

I think this sounds like a good plan.

kstefanj

Nice to see this unified. Some comments below.

kstefanj · 2021-12-01T15:11:15Z

src/hotspot/share/gc/shared/blockOffsetTable.hpp

+  static uint _log_bot_card_size;
+  static uint _log_bot_card_size_words;
+  static uint _bot_card_size_bytes;
+  static uint _bot_card_size_words;


Maybe change words to in_words to better match other places where we have sizes in words. And as Thomas suggested above, maybe also drop the bot in/pre-fix.

And also change the getters below.

kstefanj · 2021-12-01T15:11:15Z

src/hotspot/share/gc/parallel/objectStartArray.hpp

+  static uint _block_shift;
+  static uint _block_size;
+  static uint _block_size_in_words;
+


I think this sounds like a good plan.

albertnetymk

Just a very minor comment.

albertnetymk · 2021-12-03T12:27:51Z

src/hotspot/share/gc/parallel/objectStartArray.cpp

 }

 void ObjectStartArray::initialize(MemRegion reserved_region) {
  // We're based on the assumption that we use the same
  // size blocks as the card table.
-  assert((int)block_size == (int)CardTable::card_size, "Sanity");
-  assert(block_size <= MaxBlockSize, "block_size must be less than or equal to " UINT32_FORMAT, MaxBlockSize);
+  assert((int)_card_size == (int)(CardTable::card_size()), "Sanity");


I think the int cast can be dropped; both sides are uint.

openjdk · 2021-12-03T12:29:14Z

@vish-chan This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8277372: Add getters for BOT and card table members

Reviewed-by: tschatzl, sjohanss, ayang

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 18 new commits pushed to the master branch:

2b87c2b: 8277793: Support vector F2I and D2L cast operations for X86
e1cde19: 8278247: KeyStoreSpi::engineGetAttributes does not throws KeyStoreException
a729a70: 8225181: KeyStore should have a getAttributes method
38f525e: 8275821: Optimize random number generators developed in JDK-8248862 using Math.unsignedMultiplyHigh()
780b8b1: 8278179: Enable all doclint warnings for build of java.naming
678ac58: 8278240: ProblemList containers/docker/TestJcmd.java on linux-aarch64
01cb2b9: 8277529: SIGSEGV in C2 CompilerThread Node::rematerialize() compiling Packet::readUnsignedTrint
660f21a: 8278119: ProblemList few headful test failing in macosx12-aarch64 system
2e30fa9: 8278171: [vectorapi] Mask incorrectly computed for zero extending cast
fbf096e: 8251400: Fix incorrect addition of library to test in JDK-8237858
... and 8 more: https://git.openjdk.java.net/jdk/compare/dda8f26ce0d2b54ef78b74b82e58255aca80576a...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@tschatzl, @kstefanj, @albertnetymk) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

tschatzl

Lgtm.

vish-chan · 2021-12-03T20:20:55Z

/integrate

openjdk · 2021-12-03T20:23:42Z

@vish-chan
Your change (at version 35112e6) is now ready to be sponsored by a Committer.

vish-chan · 2021-12-06T05:46:41Z

@tschatzl is there anything else required from my end?

tschatzl · 2021-12-06T15:26:18Z

/sponsor
Thanks @vish-chan for fixing all this.

openjdk · 2021-12-06T15:28:31Z

Going to push as commit adf3952.
Since your change was applied there have been 33 commits pushed to the master branch:

7c6f57f: 8275610: C2: Object field load floats above its null check resulting in a segfault
a885aab: 8276125: RunThese24H.java SIGSEGV in JfrThreadGroup::thread_group_id
6994d80: 8278291: compiler/uncommontrap/TraceDeoptimizationNoRealloc.java fails with release VMs after JDK-8154011
286a26c: 8278277: G1: Simplify implementation of G1GCPhaseTimes::record_or_add_time_secs
d14f06a: 8278031: MultiThreadedRefCounter should not use relaxed atomic decrement
8d190dd: 8277496: Remove duplication in c1 Block successor lists
194cdf4: 8277864: Compilation error thrown while doing a boxing conversion on selector expression
f39fe5b: 8154011: Make TraceDeoptimization a diagnostic flag
f180a45: 8278016: Add compiler tests to tier{2,3}
104aa1f: 8268575: Annotations not visible on model elements before they are generated
... and 23 more: https://git.openjdk.java.net/jdk/compare/dda8f26ce0d2b54ef78b74b82e58255aca80576a...master

Your commit was automatically rebased without conflicts.

openjdk · 2021-12-06T15:28:53Z

@tschatzl @vish-chan Pushed as commit adf3952.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

Initial patch

1ffc2d3

openjdk bot added the rfr label Nov 26, 2021

openjdk bot added the hotspot label Nov 26, 2021

Refactoring in hotspot/cpu dir

bb85aa4

tschatzl suggested changes Nov 29, 2021

View changes

vish-chan added 2 commits Nov 30, 2021

Merge branch 'master' into JDK-8277372-refactor

69ee4a3

Rename BOTConstants

4882887

tschatzl suggested changes Nov 30, 2021

View changes

kstefanj suggested changes Dec 1, 2021

View changes

vish-chan added 2 commits Dec 2, 2021

Rename BOTConstants and ObjectStartArray members to _card_*

168e34e

Merge branch 'master' into JDK-8277372-refactor

0f63516

albertnetymk approved these changes Dec 3, 2021

View changes

openjdk bot added the ready label Dec 3, 2021

kstefanj approved these changes Dec 3, 2021

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Change to address @albertnetymk comment

35112e6

tschatzl approved these changes Dec 3, 2021

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openjdk bot added the sponsor label Dec 3, 2021

openjdk bot closed this Dec 6, 2021

openjdk bot added the integrated label Dec 6, 2021

openjdk bot removed ready rfr sponsor labels Dec 6, 2021

vish-chan deleted the JDK-8277372-refactor branch Jan 13, 2022

8277372: Add getters for BOT and card table members #6570

8277372: Add getters for BOT and card table members #6570

vish-chan commented Nov 26, 2021 •

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openjdk bot commented Dec 6, 2021

	(u_char) (BOTConstants::bot_card_size_words()+BOTConstants::N_powers-1),
	(u_char) (BOTConstants::bot_card_size_words() + BOTConstants::N_powers - 1),

	(uint) (BOTConstants::bot_card_size_words()+BOTConstants::N_powers-1));
	(uint) (BOTConstants::bot_card_size_words() + BOTConstants::N_powers - 1));

	dirty_cards*_card_size_in_words);
	dirty_cards * _card_size_in_words);

8277372: Add getters for BOT and card table members #6570

8277372: Add getters for BOT and card table members #6570

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vish-chan commented Nov 26, 2021 • edited by openjdk[bot] bot

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Webrevs

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