RFR: 8324646: Avoid Class.forName in SecureRandom constructor

[Aleksey Shipilev]

On Wed, 24 Jan 2024 15:25:28 GMT, Oli Gillespie <ogillespie at openjdk.org> wrote:

> Avoid expensive `Class.forName` call when constructing Providers such as `SecureRandom` which take constructor parameters. This can easily be cached in EngineDescription (this cache already existed before, it was removed in [JDK-8280970](https://bugs.openjdk.org/browse/JDK-8280970) as unused, I'm bringing it back unchanged to support this new usage).
> 
> Benchmark results on my Linux x86 host show around a 20% reduction in time to create a new `SecureRandom` instance. Most of the remaining overhead is due to a failing constructor lookup - see [JDK-8324648](https://bugs.openjdk.org/browse/JDK-8324648).
> 
> 
> Before
> newSecureRandom  avgt  2930 ± 50  ns/op
> 
> After
> newSecureRandom  avgt  2400 ± 33  ns/op
> 
> 
> I have seen multiple real-world applications which call `new SecureRandom()` on the hot path, so I believe efficiency here is important.

This looks promising to me! But we need to polish this a bit:

src/java.base/share/classes/java/security/Provider.java line 1560:

> 1558:         final boolean supportsParameter;
> 1559:         final String constructorParameterClassName;
> 1560:         private volatile Class<?> constructorParameterClass;

Style: no need for `private` here, match what other fields are doing.

src/java.base/share/classes/java/security/Provider.java line 1568:

> 1566:         }
> 1567: 
> 1568:         Class<?> getConstructorParameterClass() throws ClassNotFoundException {

I think we want to do what `Service.getImplClass` is doing, for extra safety: retain cached class on a `WeakReference`. This would avoid accidental class leakage in this code.

src/java.base/share/classes/java/security/Provider.java line 1909:

> 1907:                 } else {
> 1908:                     ctrParamClz = cap.constructorParameterClassName == null?
> 1909:                         null : cap.getConstructorParameterClass();

Maybe we should move the ternary for `cap.constructorParameterClassName == null` into new method to begin with.

test/micro/org/openjdk/bench/java/security/SecureRandomBench.java line 1:

> 1: package org.openjdk.bench.java.security;

No copyright header?

test/micro/org/openjdk/bench/java/security/SecureRandomBench.java line 16:

> 14: 
> 15:     @Benchmark
> 16:     public SecureRandom newSecureRandom() throws Exception {

Just "create()", I think. No need to repeat it with `SecureRandomBench.newSecureRandom`.

-------------

PR Review: https://git.openjdk.org/jdk/pull/17559#pullrequestreview-1842025562
PR Review Comment: https://git.openjdk.org/jdk/pull/17559#discussion_r1465331538
PR Review Comment: https://git.openjdk.org/jdk/pull/17559#discussion_r1465330794
PR Review Comment: https://git.openjdk.org/jdk/pull/17559#discussion_r1465332784
PR Review Comment: https://git.openjdk.org/jdk/pull/17559#discussion_r1465332949
PR Review Comment: https://git.openjdk.org/jdk/pull/17559#discussion_r1465334379