8255917: runtime/cds/SharedBaseAddress.java failed "assert(reserved_rgn != 0LL) failed: No reserved region" #1750

yminqi · 2020-12-11T20:06:34Z

Hi, Please review
(This is redo for #1657)
Windows mapping for file into memory could not happen to reserved memory. In mapping CDS archive we first reserve enough memory then before mapping, release them. For cds archive and using class space, need split the whole space into two spaces. To do so, we need release the whole first then do the reserve again on the split, which is problematic that there is possibility other thread or system can kick in to take the released space.
The fix is the first step of two steps:

Do not split reserved memory;
Remove splitting memory.
This fix is first step, for Windows and use requested mapping address, reserved for cds archive and ccs on a contiguous space separately, so there is no need to call split. If any reservation failed, go to other way, but do not do the 'real' split for the whole reserved space, keep the whole region reserved and released as a whole.
Also fixed issues that when loading shared archive failed, bitmap region should be unmapped or it will cause mismatch in reserved/committed size calculation for NMT.
Fixed reserved region name for adding committed region for NMT, it should use the reserved region name not "Unknown" the default.
A test case added for testing the failed case which is caused by mismatch of class path.

Tests:tier1-5,tier7

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Issue

JDK-8255917: runtime/cds/SharedBaseAddress.java failed "assert(reserved_rgn != 0LL) failed: No reserved region"

Reviewers

Calvin Cheung (@calvinccheung - Reviewer)
Ioi Lam (@iklam - Reviewer)
Thomas Stuefe (@tstuefe - Reviewer)

Download

$ git fetch https://git.openjdk.java.net/jdk pull/1750/head:pull/1750
$ git checkout pull/1750

…gn != 0LL) failed: No reserved region"

bridgekeeper · 2020-12-11T20:06:45Z

👋 Welcome back minqi! 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 · 2020-12-11T20:07:53Z

@yminqi 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 · 2020-12-11T20:11:08Z

Webrevs

calvinccheung · 2020-12-12T00:02:31Z

test/hotspot/jtreg/runtime/cds/appcds/MismatchedPathTriggerMemoryRelease.java

+ * @requires vm.cds
+ * @library /test/lib
+ * @compile test-classes/Hello.java
+ * @run main/timeout=240 MismatchedPathTriggerMemoryRelease


Does this test requires more than the default timeout (120s) to run?

Does this test requires more than the default timeout (120s) to run?
No, I will fix it. Thanks.

calvinccheung · 2020-12-12T00:45:23Z

test/hotspot/jtreg/runtime/cds/appcds/MismatchedPathTriggerMemoryRelease.java

+        execOutput = TestCommon.exec("non-exist.jar",
+                                     "-Xshare:auto",
+                                     "-Xlog:os,cds=debug",
+                                     "-XX:NativeMemoryTracking=detail",
+                                     "-XX:SharedBaseAddress=0",
+                                     "Hello");


Instead of TestCommon.exec, you could use TestCommon.execAuto and no need to pass the -Xshare:auto argument.

Changed to execAuto, remove "-Xshare:auto", it failed on "Error: Could not find or load main class non-exist.jar" so i will keep original version.

I think you'll need to add "-cp" before "non-exist.jar" for execAuto to work.
I'm fine to leave it as is.

calvinccheung

One more comment regarding the test. Up to you if you want to make the change.

iklam · 2020-12-14T06:57:54Z

src/hotspot/share/runtime/os.cpp

    res = pd_release_memory(addr, bytes);
  }
+  if (!res) {
+    log_info(os)("os::release_memory(" PTR_FORMAT ", " SIZE_FORMAT ") failed", p2i(addr), bytes);


I think it's better to use "os::release_memory failed (" PTR_FORMAT ", " SIZE_FORMAT ")". That way it's easy to match the error message in the test case with a simple substring test of "os::release_memory failed". Otherwise it's hard to see that the regexp in the test "os::release_memory\$0x[0-9a-fA-F]*,\\s[0-9]*\$\\sfailed" indeed would match the error message.

Thanks for the suggestion. Will make the check in test simple. (I have tested the pattern using online java pattern match and a local test program for it).

Thanks
Yumin

…ing the message

iklam

LGTM

openjdk · 2020-12-14T18:43:15Z

@yminqi 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:

8255917: runtime/cds/SharedBaseAddress.java failed "assert(reserved_rgn != 0LL) failed: No reserved region"

Reviewed-by: ccheung, iklam, stuefe

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 24 new commits pushed to the master branch:

568dc29: 8185734: [Windows] Structured Exception Catcher missing around gtest execution
3ab1dfe: 8257828: SafeFetch may crash if invoked in non-JavaThreads
381021a: Merge
afc4441: 8258094: AIX build fails after 8257602
164c8a6: 8258092: Link to early access platform documentation in TestHtmlTableTags.java
43dc3f7: 8254350: CompletableFuture.get may swallow InterruptedException
6d79ec8: 8258111: Problemlist compiler/blackhole tests for -Xcomp until JDK-8258101 is fixed
2001da3: 8257596: Clarify trusted final fields for record classes
b1afed7: 8257919: [JVMCI] profiling info didn't change after reprofile
b7ac32d: 8257598: Clarify what component values are used in Record::equals
... and 14 more: https://git.openjdk.java.net/jdk/compare/f9c9bf03a80a5b30319fedcc716cdf93fb74afec...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.

calvinccheung

Looks good.

yminqi · 2020-12-14T19:14:32Z

@iklam @calvinccheung Thanks for review. I will wait for @tstuefe input for integration.

tstuefe · 2020-12-14T19:56:58Z

Hi Yumin,

I don't understand the special handling in NMT.

Unix: We reserve a region, split it, tell NMT about the split (see posix version of os::split_reserved_memory), then later release both parts separately.
Windows:

use_archive_base_addr = true: we allocate the spaces separately, later release them separately
use_archive_base_addr = false: we allocate total space, leave it unsplit, then later release the total space.

Where is this new NMT coding needed?

Thanks, Thomas

yminqi · 2020-12-14T20:12:06Z

Hi, Thomas

I don't understand the special handling in NMT.

Unix: We reserve a region, split it, tell NMT about the split (see posix version of os::split_reserved_memory), then later release both parts separately.
There is no problem for Linux/Unix here since split does not do the split.
Windows:

use_archive_base_addr = true: we allocate the spaces separately, later release them separately
Yes, the two spaces are released separately and NMT will find exact matched regions to remove.

use_archive_base_addr = false: we allocate total space, leave it unsplit, then later release the total space.

The space reserved as a whole, and we did not do the 'split' on it. The release should be on whole too. When unmapping regions, the released on region in fact did not do anything in nmt since it is within the archive space. Since the new code is release on the whole space (there is no call to release on class_space_rs in this case), so it check if it is > archive_space_rs (with tag of mtClassShared) we know it is for releasing the whole space. The space which is bigger than archive_space_rs with tag of mtClassShared should be only the whole space.

Where is this new NMT coding needed?

The code is to make the bytes in snapshot correct. That, when all the spaces release, the bytes in the reserved slot should be 'zero'.

Thanks for review.

tstuefe · 2020-12-15T09:43:47Z

Hi, Thomas

I don't understand the special handling in NMT.
Unix: We reserve a region, split it, tell NMT about the split (see posix version of os::split_reserved_memory), then later release both parts separately.
There is no problem for Linux/Unix here since split does not do the split.
Windows:

use_archive_base_addr = true: we allocate the spaces separately, later release them separately
Yes, the two spaces are released separately and NMT will find exact matched regions to remove.

use_archive_base_addr = false: we allocate total space, leave it unsplit, then later release the total space.

The space reserved as a whole, and we did not do the 'split' on it. The release should be on whole too. When unmapping regions, the released on region in fact did not do anything in nmt since it is within the archive space. Since the new code is release on the whole space (there is no call to release on class_space_rs in this case), so it check if it is > archive_space_rs (with tag of mtClassShared) we know it is for releasing the whole space. The space which is bigger than archive_space_rs with tag of mtClassShared should be only the whole space.

Okay. Lets see if I understand:

For (2) and for Unix, we reserve the total area. Then we tell NMT to semantically split it up in two regions (MemTracker::record_virtual_memory_split_reserved...) - later we tag the first one with "mtClassShared", the second with "mtClass". Then, if initializing the archive fails, we release now the total area. Since NMT has only the split view, it finds the mtClassShared entry at base address which is of smaller size. We run into the if (size > reserved_rgn->size()) { case in virtualMemoryTracker.cpp:517. We release both separately.

Right?

Also: the section at virtualMemoryTracker.cpp:509 if (reserved_rgn->contain_region(addr, size)) { should only be needed for Posix, right? We never should run into the problem that we unmap a section within another section on Windows? So, in theory, we should be able to make this a WINDOWS_ONLY(ShouldNotReachHere()) ?

--

Going forward, I wonder whether NMT should have general support for releasing multiple mappings in one go. Since we introduced the concept of "artificial split" with MemTracker::record_virtual_memory_split_reserved... we may want to have now a corresponding "multi-release". Or, Idk, maybe just remove the MemTracker::record_virtual_memory_split_reserved and the corresponding code in NMT release? and just live with the fact that for a "shallow split" the numbers in NMT are accounted to the wrong tag (mtClassShared gets mtClass).

Where is this new NMT coding needed?

The code is to make the bytes in snapshot correct. That, when all the spaces release, the bytes in the reserved slot should be 'zero'.

Thanks for review.

The rest looks good AFAICS.

For JDK17, I really hope we can simplify and streamline this coding. Maybe if we consider one or two things:

just do File IO always on Windows? I did make a test and I may be wrong but I could not measure any startup performance loss compared to the multiple mappings.
instead of many little mmap calls, just mmap the whole archive right at reservation time alongside the class space reservation. That would increase the chance that everything goes well, and reduce the complexity of the cleanup if it doesn't.

What do you think, does that make sense?

Thanks, Thomas

tstuefe

LGTM

yminqi · 2020-12-15T15:46:21Z

@tstuefe Thanks for review, next os::split_reserved_memory will be removed (https://bugs.openjdk.java.net/browse/JDK-8256213).

yminqi · 2020-12-15T16:51:56Z

/integrate

openjdk · 2020-12-15T16:52:49Z

@yminqi Since your change was applied there have been 27 commits pushed to the master branch:

d53ee62: 8255899: Allow uninstallation of jpackage exe bundles
65756ab: 8257802: LogCompilation throws couldn't find bytecode on JDK 8 log
a372be4: 8258244: Shenandoah: Not expecting forwarded object in roots during mark after JDK-8240868
568dc29: 8185734: [Windows] Structured Exception Catcher missing around gtest execution
3ab1dfe: 8257828: SafeFetch may crash if invoked in non-JavaThreads
381021a: Merge
afc4441: 8258094: AIX build fails after 8257602
164c8a6: 8258092: Link to early access platform documentation in TestHtmlTableTags.java
43dc3f7: 8254350: CompletableFuture.get may swallow InterruptedException
6d79ec8: 8258111: Problemlist compiler/blackhole tests for -Xcomp until JDK-8258101 is fixed
... and 17 more: https://git.openjdk.java.net/jdk/compare/f9c9bf03a80a5b30319fedcc716cdf93fb74afec...master

Your commit was automatically rebased without conflicts.

Pushed as commit 36e2097.

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

8255917: runtime/cds/SharedBaseAddress.java failed "assert(reserved_r…

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…gn != 0LL) failed: No reserved region"

openjdk bot added the rfr Pull request is ready for review label Dec 11, 2020

openjdk bot added the hotspot hotspot-dev@openjdk.org label Dec 11, 2020

calvinccheung reviewed Dec 12, 2020

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Use default timeout number (120) for the test

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iklam suggested changes Dec 14, 2020

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Fixed os::release message to make test simply check if output contain…

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yminqi deleted the jdk-8255917 branch December 15, 2020 17:48

8255917: runtime/cds/SharedBaseAddress.java failed "assert(reserved_rgn != 0LL) failed: No reserved region" #1750

8255917: runtime/cds/SharedBaseAddress.java failed "assert(reserved_rgn != 0LL) failed: No reserved region" #1750

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