8310743: assert(reserved_rgn != nullptr) failed: Add committed region, No reserved region found #14730

xmas92 · 2023-06-30T13:07:17Z

JDK-8309675 tried to solve the issue of NMT reporting to much committed memory by faking the virtual addresses registered when committing physical memory. This mapping was simply the virtual address = physical offset in backing file + heap base. This works when ZGC gets a contiguous heap which starts at the heap base. However fails if it does not start at the heap base or is discontiguous.

This proposal fixes this by keeping track of all the reserved virtual address ranges and by creating a mapping from the physical offsets to the actual reserved virtual address ranges. If the physical offsets committed maps to multiple reserved ranges, it is processed as multiple commits.

The develop flag ZForceDiscontiguousHeapReservations is introduced to test the discontiguous heap feature and interactions.

Testing:

Added test on all Oracle platforms
GHA
Running tier1-3

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Issue

JDK-8310743: assert(reserved_rgn != nullptr) failed: Add committed region, No reserved region found (Bug - P2)

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Stefan Karlsson (@stefank - Reviewer)
Albert Mingkun Yang (@albertnetymk - Reviewer)

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…, No reserved region found

bridgekeeper · 2023-06-30T13:08:56Z

👋 Welcome back aboldtch! 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 · 2023-06-30T13:12:09Z

@xmas92 The following label will be automatically applied to this pull request:

hotspot-gc

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.

openjdk · 2023-06-30T13:15:12Z

@xmas92 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:

8310743: assert(reserved_rgn != nullptr) failed: Add committed region, No reserved region found

Reviewed-by: stefank, 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 34 new commits pushed to the master branch:

ba974d5: 8310661: JFR: Replace JVM.getJVM() with JVM
496f94b: 8311086: Remove jtreg/gc/startup_warnings
9d2e0b2: 8307934: JRobot.moveMouseTo must access component on EDT
87c79c0: 8309302: java/net/Socket/Timeouts.java fails with AssertionError on test temporal post condition
8e0ca8e: 8310331: JitTester: Exclude java.lang.Math.random
055b4b4: 8310948: Fix ignored-qualifiers warning in Hotspot
2c29705: 8309660: C2: failed: XMM register should be 0-15 (UseKNLSetting and ConvF2HF)
52ee570: 8309209: C2 failed "assert(_stack_guard_state == stack_guard_reserved_disabled) failed: inconsistent state"
faf1b82: 8310656: RISC-V: __builtin___clear_cache can fail silently.
0e3d91d: 8311215: [BACKOUT] JDK-8047998 Abort the vm if MaxNewSize is not the same as NewSize when MaxHeapSize is the same as InitialHeapSize
... and 24 more: https://git.openjdk.org/jdk/compare/07734f6dde2b29574b6ef98eeb9e007d8801a3ea...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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

mlbridge · 2023-06-30T13:19:17Z

Webrevs

00: Full (8cf2bf77)

albertnetymk · 2023-06-30T13:45:23Z

src/hotspot/share/gc/z/zNMT.cpp

+  for (; index < _num_reservations; ++index) {
+    const size_t reservation_size = _reservations[index]._size;
+    if (*offset_in_reservation < reservation_size) {
+      break;


I wonder if one can return index here. Then, after the for-loop, one can write fatal(...).

It was purposely written like this avoiding a fatal/guarantee/ShouldNotReachHere, the intent is to have bugs only be caught in debug. If we return _num_reservations as an index all that happens is that we do not register some commit with nmt. Which seems more favourable than crashing if some bug were to slip through into production.

albertnetymk · 2023-06-30T15:12:55Z

src/hotspot/share/gc/z/zNMT.cpp

+    offset_in_reservation = 0;
+  }
+
+  assert(left_to_process == 0, "everything was not commited");


When will this be reachable? I'd expect the if-check inside the for-loop to handle exit-condition.

If we run out of reservations. That is the virtual memory reservations range is less than the physical memory offset we are committing. Such a thing should not be reachable and is a bug. But if it does happen it should be caught here.

albertnetymk · 2023-06-30T15:14:48Z

src/hotspot/share/gc/z/zNMT.cpp

+      if (MemTracker::enabled()) {
+        Tracker tracker(Tracker::uncommit);
+        tracker.record((address)sub_range_addr, sub_range_size);
+      }


Sth like record_virtual_memory_uncommit would make this more symmetric. (Better be done in a followup PR though.)

I agree. Purposely kept this minimal as it needs to be backported to 21.

albertnetymk

I think it's better to fail-early when sth unexpected occurs, so both places warrant a should-not-reach-here; subjective though.

xmas92 · 2023-07-03T14:06:03Z

I generally agree with the fail early strategy. My personal ILW assessment of the two approaches made me favour this one. But maybe I'll reassess this in the future.

Thanks for all reviews.

/integrate

openjdk · 2023-07-03T14:07:02Z

Going to push as commit f393975.
Since your change was applied there have been 34 commits pushed to the master branch:

ba974d5: 8310661: JFR: Replace JVM.getJVM() with JVM
496f94b: 8311086: Remove jtreg/gc/startup_warnings
9d2e0b2: 8307934: JRobot.moveMouseTo must access component on EDT
87c79c0: 8309302: java/net/Socket/Timeouts.java fails with AssertionError on test temporal post condition
8e0ca8e: 8310331: JitTester: Exclude java.lang.Math.random
055b4b4: 8310948: Fix ignored-qualifiers warning in Hotspot
2c29705: 8309660: C2: failed: XMM register should be 0-15 (UseKNLSetting and ConvF2HF)
52ee570: 8309209: C2 failed "assert(_stack_guard_state == stack_guard_reserved_disabled) failed: inconsistent state"
faf1b82: 8310656: RISC-V: __builtin___clear_cache can fail silently.
0e3d91d: 8311215: [BACKOUT] JDK-8047998 Abort the vm if MaxNewSize is not the same as NewSize when MaxHeapSize is the same as InitialHeapSize
... and 24 more: https://git.openjdk.org/jdk/compare/07734f6dde2b29574b6ef98eeb9e007d8801a3ea...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-07-03T14:07:14Z

@xmas92 Pushed as commit f393975.

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

8310743: assert(reserved_rgn != nullptr) failed: Add committed region…

8cf2bf7

…, No reserved region found

openjdk bot added the rfr Pull request is ready for review label Jun 30, 2023

openjdk bot added the hotspot-gc hotspot-gc-dev@openjdk.org label Jun 30, 2023

stefank approved these changes Jun 30, 2023

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albertnetymk reviewed Jun 30, 2023

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xmas92 deleted the JDK-8310743 branch January 5, 2026 06:11

8310743: assert(reserved_rgn != nullptr) failed: Add committed region, No reserved region found #14730

8310743: assert(reserved_rgn != nullptr) failed: Add committed region, No reserved region found #14730

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