8357570: [macOS] os::Bsd::available_memory() might return too low values

[MBaesken]

Currently os::Bsd::available_memory() returns on macOS
vmstat.free_count * os::vm_page_size();
But just using free_count is rather conservative because there are other memory categories on macOS that can be made available too. Unfortunately the different memory categories
There is a bit of additional information here https://developer.apple.com/forums/thread/118867
that confirms that free memory / free_count is only a fraction of what is available.

There is also some info here
https://developer.apple.com/library/archive/documentation/Performance/Conceptual/ManagingMemory/Articles/AboutMemory.html#//apple_ref/doc/uid/20001880-BCICIHAB
containing this relevant info :
"The inactive list contains pages that are currently resident in physical memory but have not been accessed recently. These pages contain valid data but may be removed from memory at any time. The free list contains pages of physical memory that are not associated with any address space of VM object. These pages are available for immediate use by any process that needs them."

and also about purgeable memory at
https://developer.apple.com/library/archive/documentation/Performance/Conceptual/ManagingMemory/Articles/CachingandPurgeableMemory.html#//apple_ref/doc/uid/TP40013104-SW1

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8357570: [macOS] os::Bsd::available_memory() might return too low values (Bug - P4)

Reviewers

• Christoph Langer (@RealCLanger - Reviewer)
• Martin Doerr (@TheRealMDoerr - Reviewer)
• Lutz Schmidt (@RealLucy - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/25657/head:pull/25657
$ git checkout pull/25657

Update a local copy of the PR:
$ git checkout pull/25657
$ git pull https://git.openjdk.org/jdk.git pull/25657/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 25657

View PR using the GUI difftool:
$ git pr show -t 25657

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/25657.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back mbaesken! 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]

@MBaesken 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:

8357570: [macOS] os::Bsd::available_memory() might return too low values

Reviewed-by: clanger, mdoerr, lucy

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 79 new commits pushed to the master branch:

• 42ab8fc: 8265754: Move suspend/resume API from HandshakeState
• bf7d40d: 8356751: IGV: clean up redundant field _should_send_method
• 5ae32c4: 8352149: Test java/awt/Frame/MultiScreenTest.java fails: Window list is empty
• ... and 76 more: https://git.openjdk.org/jdk/compare/4e314cb9e025672b2f7b68cc021fa516ee219ad8...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.

[openjdk]

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

• hotspot-runtime

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]

Webrevs

• 00: Full (b4bb986c)

[RealCLanger]

Looking at the linked documentation this seems to make sense, although I have no means to check plausibility.

Maybe the comment before os::Bsd::available_memory could be modified/weakened a little bit because with the updated gathering it might be of some more use now... 😉

[TheRealMDoerr]

LGTM. But I'm not a memory management expert.

[RealLucy]

LGTM.
The cited documentation suggests the fix is ok.

[MBaesken]

Thanks for the reviews !

/integrate

[openjdk]

Going to push as commit 7d7fc69.
Since your change was applied there have been 79 commits pushed to the master branch:

• 42ab8fc: 8265754: Move suspend/resume API from HandshakeState
• bf7d40d: 8356751: IGV: clean up redundant field _should_send_method
• 5ae32c4: 8352149: Test java/awt/Frame/MultiScreenTest.java fails: Window list is empty
• ... and 76 more: https://git.openjdk.org/jdk/compare/4e314cb9e025672b2f7b68cc021fa516ee219ad8...master

Your commit was automatically rebased without conflicts.

[openjdk]

@MBaesken Pushed as commit 7d7fc69.

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