Use pointer tagging to avoid clearing chunks at start of GC #4364
Conversation
This file contains 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
As part of ponylang#4143, the logic was changed to avoid clearing chunks at the start of GC (except for sizeclass 0) by using a sentinel value in the `chunk->shallow` field. This commit, changes the implementation to rely on pointer tagging of the `chunk->m` field using the lowest bit to track whether a chunk needs to be cleared or not. The sentinel in the `chunk->shallow` is no longer needed/used allowing for this optimization to work for all sizeclasses (including the previously excluded sizeclass 0). All accesses to the `chunk->m` field now go through the utility function `get_m` to clear out the tagged bit first.
ponylang-main
added
the
discuss during sync
ponylang-main
removed
the
discuss during sync
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
As part of #4143, the logic was changed to avoid clearing chunks at the start of GC (except for sizeclass 0) by using a sentinel value in the
chunk->shallowfield.This commit, changes the implementation to rely on pointer tagging of the
chunk->mfield using the lowest bit to track whether a chunk needs to be cleared or not. The sentinel in thechunk->shallowis no longer needed/used allowing for this optimization to work for all sizeclasses (including the previously excluded sizeclass 0). All accesses to thechunk->mfield now go through the utility functionget_mto clear out the tagged bit first.