JDK-8304820: Statically allocate ObjectSynchronizer mutexes #13160

jcking · 2023-03-23T15:53:28Z

Similar to https://git.openjdk.org/jdk/pull/13143, statically allocate mutexes which live for the lifetime of the process.

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Issue

JDK-8304820: Statically allocate ObjectSynchronizer mutexes

Reviewers

Daniel D. Daugherty (@dcubed-ojdk - Reviewer)
David Holmes (@dholmes-ora - Reviewer) ⚠️ Review applies to d6afef79

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/13160/head:pull/13160
$ git checkout pull/13160

Update a local copy of the PR:
$ git checkout pull/13160
$ git pull https://git.openjdk.org/jdk.git pull/13160/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 13160

View PR using the GUI difftool:
$ git pr show -t 13160

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/13160.diff

Signed-off-by: Justin King <jcking@google.com>

bridgekeeper · 2023-03-23T15:54:44Z

👋 Welcome back jcking! 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 · 2023-03-23T15:58:50Z

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

hotspot-runtime

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mlbridge · 2023-03-23T16:03:10Z

Webrevs

src/hotspot/share/runtime/synchronizer.cpp

dcubed-ojdk · 2023-03-23T21:01:05Z

Thumbs up.

openjdk · 2023-03-23T21:02:52Z

@jcking 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:

8304820: Statically allocate ObjectSynchronizer mutexes

Reviewed-by: dcubed, dholmes

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 67 new commits pushed to the master branch:

50a995f: 8304927: Update java/net/httpclient/BasicAuthTest.java to check basic auth over HTTP/2
ca745cb: 8291598: Matcher.appendReplacement should not create new StringBuilder instances
1683a63: 8305098: [Backout] JDK-8303912 Clean up JavadocTokenizer
fab2357: 8304498: JShell does not switch to raw mode when there is no /bin/test
1fc218c: 8303912: Clean up JavadocTokenizer
c1f5ca1: 8303623: Compiler should disallow non-standard UTF-8 string encodings
695683b: 8304880: [PPC64] VerifyOops code in C1 doesn't work with ZGC
83ce65e: 8305004: add @SPEC tags to langtools modules
32ef452: 8304884: Update Bytecodes data to be mostly compile time constants
927e674: 8300977: Retire java.io.ExpiringCache
... and 57 more: https://git.openjdk.org/jdk/compare/bf917ba6af9a69859f469a1e8056fbd32396cae4...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.

jcking · 2023-03-23T21:41:59Z

/reviewers 2

openjdk · 2023-03-23T21:42:43Z

@jcking
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).

Signed-off-by: Justin King <jcking@google.com>

jcking · 2023-03-23T21:47:43Z

Hm. We may want to try placing each mutex on separate cache lines if necessary. Can be done by creating a lightweight wrapper struct which uses alignas(DEFAULT_CACHE_LINE_SIZE). Thoughts?

dholmes-ora

Seems fine.

Thanks.

jcking · 2023-03-27T14:20:04Z

Looking into the macOS odd build errors before moving forward.

Signed-off-by: Justin King <jcking@google.com>

dcubed-ojdk

Still thumbs up.

jcking · 2023-03-27T20:21:41Z

Yeah, sorry had to fix how the storage was declared. Forgot that the compiler inserts the default constructor if you use a typed array. Should be good now, waiting on GHA to confirm.

dholmes-ora · 2023-03-28T05:04:37Z

src/hotspot/share/runtime/synchronizer.cpp

+// Static storage for an array of PlatformMutex. Each entry is aligned to `alignas(PlatformMutex)`
+// by property of the storage itself being aligned to that requirement and each entry storage being
+// `sizeof(PlatformMutex)` aligned up to `alignof(PlatformMutex)`.
+alignas(PlatformMutex) static uint8_t _inflation_locks[inflation_lock_count()][align_up(sizeof(PlatformMutex), alignof(PlatformMutex))];


I'm afraid you lost me here. Why does this have to be so convoluted/obscure?

I thought sizeof(T) always was a multiple of alignof(T). Is there some case where this is not true?

Ah, I had assumed it wasn't required. But a quick glance says it is. So I'll remove the align_up. Should be more simple now.

Signed-off-by: Justin King <jcking@google.com>

dcubed-ojdk

Still good.

src/hotspot/share/runtime/synchronizer.cpp

jcking · 2023-03-30T14:27:03Z

Last call for complaints/concerns/etc. I'll wait until roughly 24 hours from now.

jcking · 2023-03-31T14:27:11Z

/integrate

openjdk · 2023-03-31T14:28:33Z

Going to push as commit fe42312.
Since your change was applied there have been 107 commits pushed to the master branch:

2f36eb0: 8305323: Update java/net/httpclient/ContentLengthHeaderTest.java to use new HttpTestServer factory methods
049b953: 8305223: IGV: mark osr compiled graphs with [OSR] in the name
345669c: 8302738: IGV: refine 'Simplify graph' filter
dea9db2: 8305055: IR check fails on some aarch64 platforms
c8f3a97: 8305171: PPC: Should use IMA::load_resolved_indy_entry() in TIG::generate_return_entry_for()
7fe5bd2: 8305174: disable dtrace for s390x builds
787832a: 8304988: unnecessary dash in @param gives double-dash in docs
a144c71: 8305008: RISC-V: Factor out immediate checking functions from assembler_riscv.inline.hpp
d815889: 8304993: bad sentence break in DateFormat
5f7b4b8: 8305111: Locale.lookupTag has typo in parameter
... and 97 more: https://git.openjdk.org/jdk/compare/bf917ba6af9a69859f469a1e8056fbd32396cae4...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-03-31T14:28:52Z

@jcking Pushed as commit fe42312.

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

Statically allocate ObjectSynchronizer mutexes

0ff0ebd

Signed-off-by: Justin King <jcking@google.com>

openjdk bot added the rfr Pull request is ready for review label Mar 23, 2023

openjdk bot added the hotspot-runtime hotspot-runtime-dev@openjdk.org label Mar 23, 2023

dcubed-ojdk approved these changes Mar 23, 2023

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openjdk bot added the ready Pull request is ready to be integrated label Mar 23, 2023

Update existing spacing since line is being touched anyway

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Signed-off-by: Justin King <jcking@google.com>

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dholmes-ora approved these changes Mar 24, 2023

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openjdk bot added the ready Pull request is ready to be integrated label Mar 24, 2023

Update approach to avoid implicit constructors

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Signed-off-by: Justin King <jcking@google.com>

dcubed-ojdk approved these changes Mar 27, 2023

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dholmes-ora reviewed Mar 28, 2023

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Remove unnecessary align_up

ff6e9d1

Signed-off-by: Justin King <jcking@google.com>

dcubed-ojdk approved these changes Mar 28, 2023

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dholmes-ora reviewed Mar 29, 2023

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openjdk bot closed this Mar 31, 2023

openjdk bot removed the ready Pull request is ready to be integrated label Mar 31, 2023

jcking deleted the objectsynchronizer-static branch March 31, 2023 14:28

openjdk bot removed the rfr Pull request is ready for review label Mar 31, 2023

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JDK-8304820: Statically allocate ObjectSynchronizer mutexes #13160

JDK-8304820: Statically allocate ObjectSynchronizer mutexes #13160

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JDK-8304820: Statically allocate ObjectSynchronizer mutexes #13160

JDK-8304820: Statically allocate ObjectSynchronizer mutexes #13160

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