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Pylance Very slow and crashing on WSL2

Open 66RED99 opened this issue 9 months ago • 5 comments

Environment data

  • Pylance version: 2025.5.1
  • OS and version: Windows 11 Pro 24H2 (Host machine), Ubuntu (WSL2)
  • Python version (& distribution if applicable, e.g. Anaconda): 3.12.3

Code Snippet

I won't be able to share the repository due to company policies, but it's a considerably large Django project.

Repro Steps

  1. The moment I start typing code, the autocomplete and syntax highlighting are extremely slow.

This issue also arose suddenly after I opened VS Code on another system (Linux Mint), as the VS Code settings were synced via cloud changes. When I returned to WSL on my Windows system, I encountered this problem.

I also noticed that the files are being analyzed from the beginning each time I type something.

Note: I do not store any of my code in the Windows file system (/mnt/c/...) . I keep it all in \\wsl.localhost\Ubuntu\home\<user>\

Expected behavior

syntax highlighting , autocomplete works as fast as before. pylance not crashing.

Actual behavior

the autocomplete and syntax highlighting are extremely slow.

Logs

2025-06-06 04:58:31.993 [info] (Client) Pylance async client (2025.5.1) started with python extension (2025.6.1)
2025-06-06 04:58:33.558 [info] [Info  - 4:58:33 AM] (839) Server root directory: file:///home/leo/.vscode-server/extensions/ms-python.vscode-pylance-2025.5.1/dist
2025-06-06 04:58:33.558 [info] [Info  - 4:58:33 AM] (839) Pylance language server 2025.5.1 (pyright version 1.1.400, commit b962ffc2) starting
2025-06-06 04:58:33.563 [info] [Info  - 4:58:33 AM] (839) Starting service instance "gts-core" for workspace "/home/leo/AgetWare/gts-core"
2025-06-06 04:58:34.345 [info] [Info  - 4:58:34 AM] (839) Loading pyproject.toml file at /home/leo/AgetWare/gts-core/pyproject.toml
2025-06-06 04:58:34.346 [info] [Info  - 4:58:34 AM] (839) Setting pythonPath for service "gts-core": "/home/leo/.virtualenvs/gt/bin/python"
2025-06-06 04:58:34.369 [info] [Info  - 4:58:34 AM] (839) No include entries specified; assuming /home/leo/AgetWare/gts-core
2025-06-06 04:58:34.370 [info] [Info  - 4:58:34 AM] (839) Auto-excluding **/node_modules
2025-06-06 04:58:34.372 [info] [Info  - 4:58:34 AM] (839) Auto-excluding **/__pycache__
2025-06-06 04:58:34.373 [info] [Info  - 4:58:34 AM] (839) Auto-excluding **/.*
2025-06-06 04:58:34.374 [info] [Info  - 4:58:34 AM] (839) Assuming Python version 3.12.3.final.0
2025-06-06 04:58:34.718 [info] [Info  - 4:58:34 AM] (839) Found 1809 source files
2025-06-06 04:58:34.736 [info] [Info  - 4:58:34 AM] (839) Loading pyproject.toml file at /home/leo/AgetWare/gts-core/pyproject.toml
2025-06-06 04:58:34.737 [info] [Info  - 4:58:34 AM] (839) Setting pythonPath for service "gts-core": "/home/leo/.virtualenvs/gt/bin/python"
2025-06-06 04:58:34.738 [info] [Info  - 4:58:34 AM] (839) No include entries specified; assuming /home/leo/AgetWare/gts-core
2025-06-06 04:58:34.739 [info] [Info  - 4:58:34 AM] (839) Auto-excluding **/node_modules
2025-06-06 04:58:34.740 [info] [Info  - 4:58:34 AM] (839) Auto-excluding **/__pycache__
2025-06-06 04:58:34.741 [info] [Info  - 4:58:34 AM] (839) Auto-excluding **/.*
2025-06-06 04:58:34.764 [info] [Info  - 4:58:34 AM] (839) Assuming Python version 3.12.3.final.0
2025-06-06 04:58:34.960 [info] [Info  - 4:58:34 AM] (839) Found 1809 source files
2025-06-06 04:58:35.736 [info] [Info  - 4:58:35 AM] (839) BG: Priority queue background worker(2) root directory: file:///home/leo/.vscode-server/extensions/ms-python.vscode-pylance-2025.5.1/dist
2025-06-06 04:58:35.736 [info] [Info  - 4:58:35 AM] (839) BG: Priority queue background worker(2) started
2025-06-06 04:58:35.736 [info] [Info  - 4:58:35 AM] (839) BG: Indexer background runner(3) root directory: file:///home/leo/.vscode-server/extensions/ms-python.vscode-pylance-2025.5.1/dist (index)
2025-06-06 04:58:35.736 [info] [Info  - 4:58:35 AM] (839) BG: Indexing(3) started
2025-06-06 04:58:39.698 [info] [Info  - 4:58:39 AM] (839) BG: [BG(1)] Long operation: analyzing: file:///home/leo/AgetWare/gts-core/notebooks/local.ipynb.py#X10sdnNjb2RlLXJlbW90ZQ%3D%3D (2238ms)
2025-06-06 04:58:39.698 [info] [Info  - 4:58:39 AM] (839) BG: scanned(3) 320 files over 1 exec env
2025-06-06 04:58:39.834 [info] [Info  - 4:58:39 AM] (839) BG: indexed(3) 320 files over 1 exec env
2025-06-06 04:58:39.908 [info] [Info  - 4:58:39 AM] (839) BG: Indexing finished(3).
2025-06-06 05:02:26.364 [info] [Info  - 5:02:26 AM] (839) Starting service instance "<default>" for workspace ""
2025-06-06 05:02:26.386 [info] [Info  - 5:02:26 AM] (839) Setting environmentName for service "<default>": "3.12.3 (gt venv)"
2025-06-06 05:02:26.387 [info] [Info  - 5:02:26 AM] (839) Setting pythonPath for service "<default>": "/home/leo/.virtualenvs/gt/bin/python"
2025-06-06 05:02:26.387 [info] [Info  - 5:02:26 AM] (839) No include entries specified; assuming /<default workspace root>
2025-06-06 05:02:26.409 [info] [Info  - 5:02:26 AM] (839) Assuming Python version 3.12.3.final.0
2025-06-06 05:02:26.453 [info] [Error - 5:02:26 AM] (839) File or directory "/<default workspace root>" does not exist.
2025-06-06 05:02:26.453 [info] [Info  - 5:02:26 AM] (839) No source files found.
2025-06-06 05:02:26.825 [info] [Info  - 5:02:26 AM] (839) BG: Priority queue background worker(5) root directory: file:///home/leo/.vscode-server/extensions/ms-python.vscode-pylance-2025.5.1/dist
2025-06-06 05:02:26.826 [info] [Info  - 5:02:26 AM] (839) BG: Priority queue background worker(5) started
2025-06-06 05:11:21.784 [info] 
<--- Last few GCs --->

[839:0x354b0310]   789785 ms: Mark-Compact 3895.9 (4138.4) -> 3882.5 (4142.8) MB, 2117.86 / 0.00 ms  (average mu = 0.069, current mu = 0.017) allocation failure; scavenge might not succeed
[839:0x354b0310]   790572 ms: Mark-Compact 3919.0 (4162.4) -> 3352.6 (4138.9) MB, 688.86 / 0.00 ms  (average mu = 0.087, current mu = 0.125) allocation failure; scavenge might not succeed


<--- JS stacktrace --->

FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory
----- Native stack trace -----


2025-06-06 05:11:21.788 [info]  1: 0xb8cf03 node::OOMErrorHandler(char const*, v8::OOMDetails const&) [/home/leo/.vscode-server/bin/258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3/node]

2025-06-06 05:11:21.788 [info]  2: 0xf04140 v8::Utils::ReportOOMFailure(v8::internal::Isolate*, char const*, v8::OOMDetails const&) [/home/leo/.vscode-server/bin/258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3/node]

2025-06-06 05:11:21.789 [info]  3: 0xf04427 v8::internal::V8::FatalProcessOutOfMemory(v8::internal::Isolate*, char const*, v8::OOMDetails const&) [/home/leo/.vscode-server/bin/258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3/node]

2025-06-06 05:11:21.789 [info]  4: 0x1116075  [/home/leo/.vscode-server/bin/258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3/node]

2025-06-06 05:11:21.789 [info]  5: 0x1116604 v8::internal::Heap::RecomputeLimits(v8::internal::GarbageCollector) [/home/leo/.vscode-server/bin/258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3/node]

2025-06-06 05:11:21.790 [info]  6: 0x112d4f4 v8::internal::Heap::PerformGarbageCollection(v8::internal::GarbageCollector, v8::internal::GarbageCollectionReason, char const*) [/home/leo/.vscode-server/bin/258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3/node]

2025-06-06 05:11:21.790 [info]  7: 0x112dd0c v8::internal::Heap::CollectGarbage(v8::internal::AllocationSpace, v8::internal::GarbageCollectionReason, v8::GCCallbackFlags) [/home/leo/.vscode-server/bin/258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3/node]

2025-06-06 05:11:21.790 [info]  8: 0x1104011 v8::internal::HeapAllocator::AllocateRawWithLightRetrySlowPath(int, v8::internal::AllocationType, v8::internal::AllocationOrigin, v8::internal::AllocationAlignment) [/home/leo/.vscode-server/bin/258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3/node]

2025-06-06 05:11:21.791 [info]  9: 0x11051a5 v8::internal::HeapAllocator::AllocateRawWithRetryOrFailSlowPath(int, v8::internal::AllocationType, v8::internal::AllocationOrigin, v8::internal::AllocationAlignment) [/home/leo/.vscode-server/bin/258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3/node]

2025-06-06 05:11:21.791 [info] 10: 0x10e27f6 v8::internal::Factory::NewFillerObject(int, v8::internal::AllocationAlignment, v8::internal::AllocationType, v8::internal::AllocationOrigin) [/home/leo/.vscode-server/bin/258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3/node]

2025-06-06 05:11:21.792 [info] 11: 0x153e336 v8::internal::Runtime_AllocateInYoungGeneration(int, unsigned long*, v8::internal::Isolate*) [/home/leo/.vscode-server/bin/258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3/node]

2025-06-06 05:11:21.792 [info] 12: 0x1977ef6  [/home/leo/.vscode-server/bin/258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3/node]

2025-06-06 05:11:47.886 [info] [Error - 5:11:47 AM] Server process exited with signal SIGABRT.
2025-06-06 05:11:47.891 [info] [Info  - 5:11:47 AM] Connection to server got closed. Server will restart.
2025-06-06 05:11:47.891 [info] true
2025-06-06 05:11:47.891 [info] [Error - 5:11:47 AM] Request textDocument/diagnostic failed.
2025-06-06 05:11:47.891 [info] Error: Starting server failed
    at P.$start (/home/leo/.vscode-server/extensions/ms-python.python-2025.6.1-linux-x64/out/client/extension.js:2:2030071)
    at P.sendRequest (/home/leo/.vscode-server/extensions/ms-python.python-2025.6.1-linux-x64/out/client/extension.js:2:2013557)
    at v.pullAsync (/home/leo/.vscode-server/extensions/ms-python.python-2025.6.1-linux-x64/out/client/extension.js:2:2077725)
2025-06-06 05:11:47.891 [info] [Error - 5:11:47 AM] Document pull failed for text document file:///home/leo/AgetWare/gts-core/gts_core/investment/managers.py
2025-06-06 05:11:47.891 [info] Error: Starting server failed
    at P.$start (/home/leo/.vscode-server/extensions/ms-python.python-2025.6.1-linux-x64/out/client/extension.js:2:2030071)
    at P.sendRequest (/home/leo/.vscode-server/extensions/ms-python.python-2025.6.1-linux-x64/out/client/extension.js:2:2013557)
    at v.pullAsync (/home/leo/.vscode-server/extensions/ms-python.python-2025.6.1-linux-x64/out/client/extension.js:2:2077725)

66RED99 avatar Jun 06 '25 05:06 66RED99

Hi @66RED99, I'm an AI Support assistant here to help with your issue. While the team reviews your request, I wanted to provide some possible tips and documentation that might help you in the meantime.

Potential Duplicate Issues – These issues may be duplicates of your report, but may differ in some of the details.

  • New indexer runs on every start and scans all site-packages and workspace files, causing sustained high CPU and slow autocomplete; workaround: exclude large folders or disable library code analysis. https://github.com/microsoft/pylance-release/issues/201
  • Performance degradation when workspace is under WSL home rather than /mnt, leading to repeated re-analysis. https://github.com/microsoft/pylance-release/issues/1443#issuecomment-867863124
  • Slowness due to remote file enumeration in WSL2 and general VS Code remote-WSL performance limitations. https://github.com/microsoft/vscode-remote-release/issues/5000

Potential Workarounds:

  • Open your project from /mnt/... instead of /home/... to leverage faster file system I/O under WSL2.

  • Create a pyrightconfig.json at your workspace root to exclude bulky directories from analysis:

    {
  "exclude": ["**/site-packages", ".pytest_cache", "node_modules"]
}

  • Disable library-code analysis to skip deep inspection of external packages:

    "python.analysis.useLibraryCodeForTypes": false

The team will respond to your issue shortly. Please note this is a trial feature and may not be fully accurate. I hope these suggestions are helpful in the meantime. If this comment helped you, please give it a 👍. If the suggestion was not helpful or was incorrect, please give it a 👎. Your feedback helps us improve!

github-actions[bot] avatar Jun 06 '25 05:06 github-actions[bot]

The crash is an out of memory situation. You could try this to alleviate the memory problem: https://github.com/microsoft/pylance-release/blob/main/TROUBLESHOOTING.md#pylance-is-crashing

You might also try excluding directories that you're not actively working on. That should make Pylance use less memory: https://github.com/microsoft/pylance-release/blob/main/docs/settings/python_analysis_exclude.md

Otherwise, we'd need a reproduction to see if we can do something about running out of memory.

rchiodo avatar Jun 06 '25 16:06 rchiodo

Found 1809 source files...seems large.. whats the name of your venv folder?

bschnurr avatar Jun 06 '25 20:06 bschnurr

Yes, it's large, but it was never this slow, nor was it crashing; this issue suddenly came up.

I use virtualenvwrapper to manage my venvs, store them in my ubuntu home\user directory \\wsl.localhost\Ubuntu\home\leo\.virtualenvs .

The name of this particular venv folder is "gt"; I'm not sure how that will help.

66RED99 avatar Jun 07 '25 05:06 66RED99

i see 'Long operation: analyzing: file:///home/leo/AgetWare/gts-core/notebooks/local.ipynb.py#X10sdnNjb2RlLXJlbW90ZQ%3D%3D (2238ms)'

try adding

  "python.analysis.logTypeEvaluationTime": true,
  "python.analysis.typeEvaluationTimeThreshold": 500,

you might be able to see the call that is taking awhile to type evaluate

bschnurr avatar Jun 07 '25 20:06 bschnurr

I was able to resolve this by reverting to extension version 2025.3.2

rcrogers avatar Jun 17 '25 20:06 rcrogers

I was also having performance issues in WSL2 and going back to 2025.5.1 fixed my issues (or seems like it did). My main issues were while working with jupiter notebooks

jbermejo-ied avatar Jun 19 '25 09:06 jbermejo-ied

one tip is to make sure your files are in WSL2 and not on windows.

bschnurr avatar Jun 19 '25 16:06 bschnurr

one tip is to make sure your files are in WSL2 and not on windows.

All my project is in WSL2

jbermejo-ied avatar Jun 23 '25 05:06 jbermejo-ied