tree 28b640381cdb05afbf1fce6c4d14f948e1a29837
parent 71404a77556d564beddc8ec53c17ddbf6c8b8ab5
author ulfjack <ulfjack@google.com> 1528814331 -0700
committer Copybara-Service <copybara-piper@google.com> 1528814405 -0700

Refactor profiler

- move the save method to an inner class
- don't use a timer, use a blocking queue instead
- add a format enum (in anticipation of adding a json output format)
- update the test to use an in memory buffer, and avoid FoundationTestCase

Compared to the original https://github.com/bazelbuild/bazel/commit/15b8c259db111012b4642287172cb4d1d82151f3, it contains these changes:
- Make it so we don't create a queue if we are not going to write any
  data! The queue is now owned by the writer, and if there is no writer, there
  is no queue.

  This was causing a memory regression because slowest task profiling is
  enabled by default, in which case the profiler is started with no output
  file. In that case, there's no thread that is emptying the queue, but the
  queue was still created by default.

- add additional tests for slowest task and histogram handling; these also
  provide coverage for the case where the profiler is started without an output
  stream
- move all the writer thread handling into the inner class
- make writer access thread-safe
- add a bunch of documentation

PiperOrigin-RevId: 200212978