C: Implement merging arena pages #719
Draft
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
timkaechele
force-pushed
the
merging-arena-pages
branch
from
58b5bf9 to
b6ab2d0
Compare
timkaechele
force-pushed
the
merging-arena-pages
branch
2 times, most recently
from
f31b7bb to
0255d2c
Compare
timkaechele
commented
Oct 23, 2025
src/util/hb_arena.c
Outdated
Comment on lines
103
to
106
| if (allocator->tail->next != NULL && hb_arena_page_has_capacity(allocator->tail->next, required_size)) { | ||
| allocator->tail = allocator->tail->next; | ||
| } else { | ||
| bool allocated = hb_arena_append_page(allocator, required_size); |
Contributor
Author
There was a problem hiding this comment.
TODO: Potential memory leak.
In a situation where the tail has a next page, but the page does not have a sufficient capacity , we would just override the page next pointer and leak the existing page that didn't have enough capacity to hold the value
Reference: append_page implementation
https://github.com/marcoroth/herb/pull/719/files#diff-38530fcdce39968fc659335346b4b6c0d6be9af0f16e2ed1354ca3bb693b2461R78
Owner
There was a problem hiding this comment.
I think that should be addressed with this: https://github.com/marcoroth/herb/compare/f1f5b6a9c95c05728ffae8dde5911aab5704010f..e1cbb82b82f97ddea4c2d61b6352a54769a0d13f
Whenever we reset to the arena to a given point we consolidate all pages that got freed up into one page, allowing us to have larger chunks of contiguous memory.
timkaechele
force-pushed
the
merging-arena-pages
branch
from
ac26b20 to
761fb2f
Compare
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Based on the arena pages proposed in #708 by @marcoroth, this PR builds on the concept and adds a more refined reset behavior that merges obsolete pages into one big page.
This has the advantage that we won't have a bunch of small pages, and instead have more contiguous memory available.
How it works
For now the first page is never deallocated and merged into a bigger page for two reasons: