Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

8267240: Bounded arena allocator doesn't work if bounded size > BLOCK_SIZE #537

Conversation

@mcimadamore
Copy link
Collaborator

@mcimadamore mcimadamore commented May 17, 2021

This patch follows the discussion in [1], and splits the unbounded allocator from the bounded one, as attempts to reusing logic were causing issues when bounded arena allocators were created with bounded size > BLOCK_SIZE.

I have looked for simplifications of the trySlice logic (also mentioned in the emails) - but in my opinion it cannot be simplified much. When an allocator is unbounded, if we receive a request that is more than half the size of the allocator block, we cannot guarantee that we can align it correctly in a segment whose size is BLOCK_SIZE. So, I think the limit of MAX_ALLOC_SIZE = BLOCK_SIZE / 2 is correct, in the sense that anything above that limit needs a standalone allocation (or we won't be able to align it in certain edge cases).

Of course, if we didn't care about alignment, the logic could be simplified, but since this is a native allocator, I think respecting alignment of the allocation request is important.

[1] - https://mail.openjdk.java.net/pipermail/panama-dev/2021-May/013796.html


Progress

  • Change must not contain extraneous whitespace
  • Change must be properly reviewed

Issue

  • JDK-8267240: Bounded arena allocator doesn't work if bounded size > BLOCK_SIZE

Reviewers

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/panama-foreign pull/537/head:pull/537
$ git checkout pull/537

Update a local copy of the PR:
$ git checkout pull/537
$ git pull https://git.openjdk.java.net/panama-foreign pull/537/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 537

View PR using the GUI difftool:
$ git pr show -t 537

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/panama-foreign/pull/537.diff

@bridgekeeper
Copy link

@bridgekeeper bridgekeeper bot commented May 17, 2021

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

@openjdk openjdk bot added the rfr label May 17, 2021
@mlbridge
Copy link

@mlbridge mlbridge bot commented May 17, 2021

Webrevs

Copy link
Member

@JornVernee JornVernee left a comment

LGTM

@mcimadamore
Copy link
Collaborator Author

@mcimadamore mcimadamore commented May 17, 2021

/integrate

@openjdk
Copy link

@openjdk openjdk bot commented May 17, 2021

@mcimadamore 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:

8267240: Bounded arena allocator doesn't work if bounded size > BLOCK_SIZE

Reviewed-by: jvernee

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 100 new commits pushed to the foreign-memaccess+abi branch:

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 foreign-memaccess+abi branch, type /integrate in a new comment.

@openjdk openjdk bot added the ready label May 17, 2021
@openjdk openjdk bot closed this May 17, 2021
@openjdk openjdk bot added integrated and removed ready rfr labels May 17, 2021
@openjdk
Copy link

@openjdk openjdk bot commented May 17, 2021

@mcimadamore Since your change was applied there have been 100 commits pushed to the foreign-memaccess+abi branch:

Your commit was automatically rebased without conflicts.

Pushed as commit 18f0e47.

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

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
2 participants