| commit | 7bad61554ec6da4ba4cbad443074360408890603 | [log] [tgz] |
|---|---|---|
| author | Michael Anthony Knyszek <mknyszek@google.com> | Thu Jun 16 20:33:35 2022 +0000 |
| committer | Michael Knyszek <mknyszek@google.com> | Thu Jun 16 21:25:35 2022 +0000 |
| tree | fd9df3023b65f581aeadb54ec0f2182cdb0c8851 | |
| parent | f38a580a51cd2fc072aabc9dd45b9e0a85064c81 [diff] |
runtime: write much more direct test for semaphore waiter scalability This test originally existed as two tests in test/locklinear.go, but this checked against actual locks and was flaky. The test was checking a property of a deep part of the runtime but from a much higher level, and it's easy for nondeterminism due to scheduling to completely mess that up, especially on an oversubscribed system. That test was then moved to the sync package with a more rigorous testing methodology, but it could still flake pretty easily. Finally, this CL makes semtable more testable, exports it in export_test.go, then writes a very direct scalability test for exactly the situation the original test described. As far as I can tell, this is much, much more stable, because it's single-threaded and is just checking exactly the algorithm we need to check. Don't bother trying to bring in a test that checks for O(log n) behavior on the other kind of iteration. It'll be perpetually flaky because the underlying data structure is a treap, so it's only _expected_ to be O(log n), but it's very easy for it to get unlucky without a large number of iterations that's too much for a simple test. Fixes #53381. Change-Id: Ia1cd2d2b0e36d552d5a8ae137077260a16016602 Reviewed-on: https://go-review.googlesource.com/c/go/+/412875 Reviewed-by: Michael Pratt <mpratt@google.com>
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