Change _stringsByHashCode to store the string.#12127
Merged
JanProvaznik merged 4 commits intodotnet:mainfrom Aug 20, 2025
Merged
Change _stringsByHashCode to store the string.#12127JanProvaznik merged 4 commits intodotnet:mainfrom
JanProvaznik merged 4 commits intodotnet:mainfrom
Conversation
Contributor
There was a problem hiding this comment.
Pull Request Overview
This PR simplifies the weak‐string caching logic by storing short strings directly in the concurrent cache and removing the extra strong‐reference path from the single‐threaded cache.
- Removed the
referencedStringfield and length check inStringWeakHandle, using only a weakGCHandle - Switched
_stringsByHashCodein the concurrent cache to hold raw strings and introduced_weakHandlesByHashCodefor long strings - Inlined and refactored
GetOrCreateEntryinto two local functions for the strong‐ and weak‐handle paths
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| src/StringTools/WeakStringCache.cs | Dropped referencedString and always uses weakHandle; removed the length constant |
| src/StringTools/WeakStringCache.Concurrent.cs | Changed strong‐string cache to ConcurrentDictionary<int, string>, refactored retrieval logic into local functions |
Comments suppressed due to low confidence (1)
src/StringTools/WeakStringCache.cs:74
- [nitpick] All strings now use a weak
GCHandle, which may introduce extra allocation and collection overhead for short strings. If preserving short‐string references was intentional, consider reintroducing a strong‐reference path for those below a length threshold.
if (weakHandle.IsAllocated)
SimaTian
approved these changes
Jul 29, 2025
Member
SimaTian
left a comment
SimaTian
left a comment
There was a problem hiding this comment.
Reasonable change in an are we recently modified - so it should be safe enough to update.
ghost
assigned
JanProvaznik
approved these changes
Aug 20, 2025
JanProvaznik
added a commit
that referenced
this pull request
Aug 26, 2025
Co-authored-by: Jan Provazník <janprovaznik@microsoft.com>
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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 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.
Fixes #
Context
The
WeakStringCacheused to store all the strings in the same dictionary, but was recently switched to use separate collections to store the longer strings that are held by weak references vs shorter strings that always used a string reference. In both cases, aStringWeakHandledwas allocated to track the value in the dictionary. This is only needed when we use a handle to track larger strings, so we can avoid the allocation in most cases and simplifyStringWeakHandlesince it no longer has to potentially store a strong reference to a string. This saves ~20MB of allocations when building Roslyn.Before:
After:
Changes Made
Testing
Notes