Per-object thread-local storage

Efficient per-object thread-local storage implementation.

Unlike thread_local crate, it will normally release the object at the end of thread. even though it will release object in other threads, but it will not let other threads use old object (see playground and document).

Unlike os-thread-local crate, it only uses the std::thread_local! abstraction of rust standard library, and does not use any other platform-related APIs. This means that its capacity is not limited by PTHREAD_KEYS_MAX.

And its performance is relatively good, value access for less than N threads is completely lock-free, and has O(1) time complexity. But since we store thread id in std::thread_local!, so we will be slightly slower than std::thread_local!.

std::thread_local!      time:   [1.5702 us 1.5725 us 1.5751 us]
                        change: [-3.6008% -0.8194% +1.2594%] (p = 0.58 > 0.05)
                        No change in performance detected.
Found 7 outliers among 100 measurements (7.00%)
  7 (7.00%) high severe

per-thread-object       time:   [1.6411 us 1.6545 us 1.6697 us]
                        change: [-0.4540% +1.1403% +2.6958%] (p = 0.16 > 0.05)
                        No change in performance detected.
Found 9 outliers among 100 measurements (9.00%)
  6 (6.00%) high mild
  3 (3.00%) high severe

thread_local            time:   [2.7854 us 2.7996 us 2.8142 us]
                        change: [-3.9626% -3.0122% -1.9548%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 4 outliers among 100 measurements (4.00%)
  2 (2.00%) high mild
  2 (2.00%) high severe

os-thread-local         time:   [1.5628 us 1.5708 us 1.5801 us]
                        change: [-2.7584% +0.1343% +3.1291%] (p = 0.94 > 0.05)
                        No change in performance detected.
Found 10 outliers among 100 measurements (10.00%)
  2 (2.00%) high mild
  8 (8.00%) high severe

License

This project is licensed under the MIT license.