Integrated: 8278241: Implement JVM SpinPause on linux-aarch64

[Evgeny Astigeevich]

On Fri, 10 Dec 2021 21:02:53 GMT, Evgeny Astigeevich <duke at openjdk.java.net> wrote:

> This JVM SpinPause uses a spin wait stub. The stub is generated based on the `SpinWait` description which is defined with `OnSpinWaitInst`/`OnSpinWaitInstCount` options.  The `SpinWait` provides the description of the instruction and the instruction count.
> 
> The `SpinWait` description is also used for the `_onSpinWait()` intrinsic. We don't have use cases when we need different implementations for the `_onSpinWait()` intrinsic and JVM SpinPause.
> 
> Testing results for fastdebug and release builds:
> - `gtest`: Passed
> - `tier1`...`tier4`: Passed
> - `hotspot/jtreg/runtime/Thread/TestSpinPause.java`: Passed
> 
> JVM SpinPause is used for the synchronised statements and can benchmarked with `org.openjdk.bench.vm.lang.LockUnlock.testContendedLock`.
> 
> Benchmarking results (number of samples per an experiment: 150) for Graviton2 (Neoverse N1), 1 ISB instruction:
> 
> 
> 
> +-----------+-------------------+------------+-----------+-----------+----------+---------+
> | CPU cores | Contended threads | Base ns/op |   Error   |    New    |  Error   |  Diff   |
> +-----------+-------------------+------------+-----------+-----------+----------+---------+
> |         8 |                64 |  10007.213 | ±910.911  |  8527.346 | ±377.242 | -14.79% |
> |        16 |                64 |  10274.935 | ±880.568  |  8310.433 | ±326.845 | -19.12% |
> |        32 |                64 |  12231.947 | ±1525.364 |  9205.941 | ±394.409 | -24.74% |
> |        64 |                64 |    9929.49 | ±586.074  | 10488.695 | ±570.458 | 5.63%   |
> |        64 |                32 |   5605.119 | ±629.340  |  5023.882 | ±230.639 | -10.37% |
> |        64 |                16 |   2817.346 | ±263.696  |  2367.528 | ±94.158  | -15.97% |
> |        64 |                 2 |    870.389 | ±530.579  |   464.395 | ±126.260 | -46.65% |
> +-----------+-------------------+------------+-----------+-----------+----------+---------+

This pull request has now been integrated.

Changeset: bcb79fd0
Author:    Evgeny Astigeevich <eastig at amazon.com>
Committer: Paul Hohensee <phh at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/bcb79fd012c9c298e58c20c59e564e9d2c16b970
Stats:     125 lines in 5 files changed: 124 ins; 0 del; 1 mod

8278241: Implement JVM SpinPause on linux-aarch64

Reviewed-by: aph, phh

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PR: https://git.openjdk.java.net/jdk/pull/6803