3 ms·

Does it re-read every single source file to find out which were changed? Sounds like a terrible approach. Or it uses mtime first and checksum after that?

• joshuamorton 4y ago
  Mtime first is unreliable on modern (fast) machines, you can edit a file twice in a single second. I think bazel has a daemon watch for file changes, but I'm not certain of that.
  • simoncion 4y ago
    ext4, btrfs, XFS all use nanosecond time resolution.
    • jpollock 4y ago
      Think remote file system where a different node is providing the mtime, so it can have substantial diffs between nodes.
    • deleted 4y ago
      [deleted]
• jxramos 4y ago
  My understanding is that somehow the bazel server tracks all that and keeps a hot process for monitoring the source files somehow to make the file io more bearable.
• oftenwrong 4y ago
  Bazel has a stateful server component that caches information about the build graph and source files in memory. As you said, this allows it to check mtimes first to avoid re-computing hashes for source files. Bazel can also read source file hashes from the filesystem if the filesystem supports it.