> Currently, to free the memory allocated in a confined arena, we keep track of > a list of 'cleanup actions', stored in linked list format in a so-called > `ResourceList`, attached to the scope of the arena. When the scope is closed, > we loop over all the entries in this resource list, and run all the cleanup > actions one by one. > > However, due to this linked list format, plus the control flow introduced by > the cleanup loop, C2's escape analysis can not keep track of the nodes of > this linked list (`ResourceList.ResourceCleanup`), and as a result, they can > not be scalar replaced. > > We can prevent just the first `ResourceCleanup` instance from escaping, by > pulling out the first element of the list into a separate field. I also tried > a setup where I had 2 separate fields for the first 2 elements, as well as a > setup with an array with a fixed set of elements. While these also worked to > prevent the first node from escaping, they were not able to provide the same > benefit for multiple resource cleanup instances. Nevertheless, avoiding the > allocation of the first element is relatively simple, and seems like a > low-hanging fruit. > > I've changed the `AllocTest` benchmark a bit so that we don't return the > `MemorySegment` in `alloc_confined`, which would make it always escape. That > way, we can use this existing benchmark to test whether there are any > allocations when calling `allocate` on a confined arena. This matches what we > were doing in the other benchmark methods in the same class.
Jorn Vernee has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision: - update copyright year - Merge branch 'master' into NoEscape - polish v2 - simplify benchmark - polish - One element cache - fix bench ------------- Changes: - all: https://git.openjdk.org/jdk/pull/23321/files - new: https://git.openjdk.org/jdk/pull/23321/files/dc386bbe..05774fc2 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=23321&range=01 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23321&range=00-01 Stats: 21481 lines in 2734 files changed: 9957 ins; 5708 del; 5816 mod Patch: https://git.openjdk.org/jdk/pull/23321.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/23321/head:pull/23321 PR: https://git.openjdk.org/jdk/pull/23321
