Unmount performance regression since 5.36.0 #16658
Description
Describe the bug
I noticed a significant increase in unmout time (during component replacement) after switching to Svelte 5.36.0 (experimental.async disabled), from 55 ms to 8.5 seconds for the dev server and up to 3 seconds for the production build.
Perhaps this is related to #16618 but i don't use stores at all.
Reproduction
- Open SJSF playground
- Pick any other example (I chose
singlein my measurements)
Performance traces for versions 5.35.7 and 5.38.3 from the dev server:
Logs
System Info
System: OS: Linux 6.12 cpe:/o:nixos:nixos:25.05 25.05 (Warbler) CPU: (12) x64 Intel(R) Core(TM) i5-10400F CPU @ 2.90GHz Memory: 6.34 GB / 15.56 GB Container: Yes Shell: 5.2.37 - /run/current-system/sw/bin/bash Binaries: Node: 24.3.0 - /nix/store/7nfklihr3idvsd18aap75mqzbwxjjg0g-nodejs-24.3.0/bin/node npm: 11.4.2 - /nix/store/7nfklihr3idvsd18aap75mqzbwxjjg0g-nodejs-24.3.0/bin/npm pnpm: 10.12.4 - /nix/store/7qxbnlds7hd3ijgq1g5gmd32gis5cabx-pnpm-10.12.4/bin/pnpm Browsers: Brave Browser: 139.1.81.131 npmPackages: svelte: catalog: => 5.38.1Severity
blocking an upgrade