chat: fix performance slowdowns when closing/reloading the window #287186
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- _onDidChangeToolsScheduler.isScheduled is checked to avoid thrashing setTimeout when disposing many tools - WorkspaceExtensionsManagementService was listening to file change events using a debounce. Debounces have overhead because a new timer is scheduled on every single call. For large amount of file changes (during EH shutdown when schemas for tools are deregistered) this caused a notable slowdown. `throttle` should be functionally equivalent. - avoid triggering input updates (w/ downstream editor effects) each time the input gets parsed, which happened every time tool is called - big hammer -- don't bother deregistering MCP tools each time Results: - `216ms` to shut down EH before making these changes - `87ms` in the first three bullets - `54ms` after skipping MCP tool deregistering. (Basically all the overhead there was unregistering the JSON schema for tool inputs.)
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Pull request overview
This PR aims to fix performance slowdowns when closing or reloading the VS Code window, specifically targeting chat and MCP tool-related overhead during Extension Host shutdown. The changes implement several optimizations to reduce shutdown time from 216ms to 54ms.
Changes:
- Replaced Event.debounce with Event.throttle for file change handling in workspace extensions management
- Added shutdown optimization to skip MCP tool cleanup during window close
- Implemented throttle event utility with comprehensive tests
- Added equals comparison for parsed chat requests to avoid redundant updates
- Optimized tool registration scheduler to prevent redundant scheduling
Reviewed changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
| src/vs/base/common/event.ts | Adds new Event.throttle utility for rate-limiting event firing |
| src/vs/base/test/common/event.test.ts | Adds comprehensive test coverage for throttle function |
| src/vs/editor/common/core/ranges/offsetRange.ts | Adds static equals method for comparing offset ranges |
| src/vs/workbench/contrib/chat/common/requestParser/chatParserTypes.ts | Adds equals method for comparing parsed chat requests |
| src/vs/workbench/contrib/chat/browser/widget/chatWidget.ts | Uses equals comparison to avoid firing redundant input change events |
| src/vs/workbench/contrib/chat/browser/tools/languageModelToolsService.ts | Checks scheduler state before scheduling to avoid redundant setTimeout calls |
| src/vs/workbench/services/extensionManagement/common/extensionManagementService.ts | Switches from debounce to throttle for file change handling |
| src/vs/workbench/contrib/mcp/common/mcpLanguageModelToolContribution.ts | Attempts to skip tool cleanup during shutdown for performance |
src/vs/workbench/contrib/mcp/common/mcpLanguageModelToolContribution.ts
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src/vs/workbench/services/extensionManagement/common/extensionManagementService.ts
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…bution.ts Co-authored-by: Copilot <[email protected]>
DonJayamanne
approved these changes
Jan 13, 2026
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throttleshould be functionally equivalent, cc @sandy081Results:
216msto shut down EH before making these changes87msin the first three bullets54msafter skipping MCP tool deregistering. (Basically all the overhead there was unregistering the JSON schema for tool inputs.)Closes #287174