perf: pre-cached indent arrays for bulk newline+spaces#676
Open
He-Pin wants to merge 2 commits intodatabricks:masterfrom
Open
perf: pre-cached indent arrays for bulk newline+spaces#676He-Pin wants to merge 2 commits intodatabricks:masterfrom
He-Pin wants to merge 2 commits intodatabricks:masterfrom
Conversation
For integer values (the common case in Jsonnet), write digits directly to CharBuilder using a scratch digit buffer instead of allocating a String via RenderUtils.renderDouble/Long.toString and copying chars. Upstream: jit branch commit d63ce90 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Pre-compute indent arrays (newline + spaces) for depths 0-15 at Renderer construction time. On flushBuffer, use bulk appendAll for the cached array instead of character-by-character space appending. Upstream: jit branch commit 4f19bde Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.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
1 participant
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
Motivation
JSON rendering produces indentation strings (newline + spaces) for every nested level. Each indent level currently allocates a new string via concatenation, creating O(depth × elements) allocations for deeply nested output.
Key Design Decision
Pre-compute and cache indent strings for each depth level in a reusable array. Subsequent renders reuse the cached strings instead of allocating new ones.
Modification
Benchmark Results
JMH (JVM, 3 iterations)
Analysis
realistic2which generates large deeply-nested JSON outputReferences
he-pin/sjsonnetjit branch indent cache optimizationResult
-10% to -18% JVM improvement by eliminating redundant indent string allocation during JSON rendering.