Commits on Aug 14, 2020

1. Set stackTraceLimit to 0 in fileSystemEntryExists …

   The exception thrown by Node.js's fs.statSync function contains a stack
   trace that can be expensive to compute. Since this exception isn't used
   by fileSystemEntryExists, we can safely set Error.stackTraceLimit to 0
   without a change in behavior.
   
   ---
   
   A significant performance improvement was noticed with this change while
   profiling tsserver on packages within a proprietary monorepo.
   Specifically, my team saw high self time percentages for Node.js's
   uvException and handleErrorFromBinding internal functions. These
   functions are executed within fs.statSync when it fails to find the
   given path.
   
   https://user-images.githubusercontent.com/906558/90183227-220cb800-dd81-11ea-8d61-f41f89481f46.png
   
   fs.statSync: https://github.com/nodejs/node/blob/v14.4.0/lib/fs.js#L1030-L1037
   handleErrorFromBinding: https://github.com/nodejs/node/blob/v14.4.0/lib/internal/fs/utils.js#L254-L269
   uvException: https://github.com/nodejs/node/blob/v14.4.0/lib/internal/errors.js#L390-L443
   
    ## Measurements
   
   After adding Error.stackTraceLimit = 0, we saw:
   
   - For a large configured project with 12,565 files, tsserver reached the
     projectLoadingFinish event 48.78% faster. (~46.786s vs ~31.447s)
   - For a medium project with 7,064 files, tsserver was 25.75% faster.
     (~20.897s vs ~16.618s)
   - For a small project with 796 files, tsserver was only a negligible
     3.00% faster. (~3.545s vs ~3.442)
   
   Measurements were taken on macOS 10.15.6, Node.js 14.4.0, and a recent
   master commit of TypeScript (610fa28). The average of 3 runs before and
   after this change were taken.
   
   I would normally include .cpuprofile and isolate-*-*-*.log files, but
   can't post them publicly in this case. If there's any other summaries
   the TypeScript team would be curious about I can report them.
   
    ## fs.statSync Misses
   
   Within our monorepo, the fs.statSync misses were mostly searches for
   alternative file extensions of module imports.
   
   - For node_modules imports, a lot of .ts/.tsx lookups failed until the
     .d.ts file was found.
   - Within projects with a lot of JSX files, .ts files were looked for
     before finding the .tsx version.
   - In the medium scale project mentioned above, a total of 38,515
     non-existent files were queried during createProgram.

   

   gluxon committed Aug 14, 2020
   Configuration menu

   • View commit details
   • Copy full SHA for 930b81c
   • Browse repository at this point

   Copy the full SHA

   930b81c View commit details

   Browse the repository at this point in the history