Re: RFR: 8330465: Stable Values and Collections (Internal) [v6]
On Thu, 16 May 2024 07:29:21 GMT, Per Minborg wrote:
>> # Stable Values & Collections (Internal)
>>
>> ## Summary
>> This PR proposes to introduce an internal _Stable Values & Collections_ API,
>> which provides immutable value holders where elements are initialized _at
>> most once_. Stable Values & Collections offer the performance and safety
>> benefits of final fields while offering greater flexibility as to the timing
>> of initialization.
>>
>> ## Goals
>> * Provide an easy and intuitive API to describe value holders that can
>> change at most once.
>> * Decouple declaration from initialization without significant footprint or
>> performance penalties.
>> * Reduce the amount of static initializer and/or field initialization code.
>> * Uphold integrity and consistency, even in a multi-threaded environment.
>>
>> For more details, see the draft JEP: https://openjdk.org/jeps/8312611
>>
>> ## Performance
>> Performance compared to instance variables using two `AtomicReference` and
>> two protected by double-checked locking under concurrent access by all
>> threads:
>>
>>
>> Benchmark Mode Cnt Score
>> Error Units
>> StableBenchmark.atomicthrpt 10259.478 ?
>> 36.809 ops/us
>> StableBenchmark.dcl thrpt 10225.710 ?
>> 26.638 ops/us
>> StableBenchmark.stablethrpt 10 4382.478 ?
>> 1151.472 ops/us <- StableValue significantly faster
>>
>>
>> Performance compared to static variables protected by `AtomicReference`,
>> class-holder idiom holder, and double-checked locking (all threads):
>>
>>
>> Benchmark Mode Cnt Score
>> Error Units
>> StableStaticBenchmark.atomic thrpt 10 6487.835 ?
>> 385.639 ops/us
>> StableStaticBenchmark.dcl thrpt 10 6605.239 ?
>> 210.610 ops/us
>> StableStaticBenchmark.stable thrpt 10 14338.239 ?
>> 1426.874 ops/us
>> StableStaticBenchmark.staticCHI thrpt 10 13780.341 ?
>> 1839.651 ops/us
>>
>>
>> Performance for stable lists (thread safe) in both instance and static
>> contexts whereby we access a single value compared to `ArrayList` instances
>> (which are not thread-safe) (all threads):
>>
>>
>> Benchmark Mode Cnt Score
>> Error Units
>> StableListElementBenchmark.instanceArrayList thrpt 10 5812.992 ?
>> 1169.730 ops/us
>> StableListElementBenchmark.instanceList thrpt 10 4818.643 ?
>> 704.893 ops/us
>> StableListElementBenchmark...
>
> Per Minborg has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Simplify exception handling and add benchmarks
src/java.base/share/classes/jdk/internal/lang/stable/StableValueImpl.java line
400:
> 398: @Override
> 399: public void run() {
> 400: stable.computeIfUnset(supplier);
We can just declare this runnable as a capturing lambda (or an anonymous class
if you fear initialization issues) and leave this comment there. The thread
field can be removed.
-
PR Review Comment: https://git.openjdk.org/jdk/pull/18794#discussion_r1603177748
Re: RFR: 8330465: Stable Values and Collections (Internal) [v6]
> # Stable Values & Collections (Internal) > > ## Summary > This PR proposes to introduce an internal _Stable Values & Collections_ API, > which provides immutable value holders where elements are initialized _at > most once_. Stable Values & Collections offer the performance and safety > benefits of final fields while offering greater flexibility as to the timing > of initialization. > > ## Goals > * Provide an easy and intuitive API to describe value holders that can > change at most once. > * Decouple declaration from initialization without significant footprint or > performance penalties. > * Reduce the amount of static initializer and/or field initialization code. > * Uphold integrity and consistency, even in a multi-threaded environment. > > For more details, see the draft JEP: https://openjdk.org/jeps/8312611 > > ## Performance > Performance compared to instance variables using two `AtomicReference` and > two protected by double-checked locking under concurrent access by all > threads: > > > Benchmark Mode Cnt Score > Error Units > StableBenchmark.atomicthrpt 10259.478 ? > 36.809 ops/us > StableBenchmark.dcl thrpt 10225.710 ? > 26.638 ops/us > StableBenchmark.stablethrpt 10 4382.478 ? > 1151.472 ops/us <- StableValue significantly faster > > > Performance compared to static variables protected by `AtomicReference`, > class-holder idiom holder, and double-checked locking (all threads): > > > Benchmark Mode Cnt Score > Error Units > StableStaticBenchmark.atomic thrpt 10 6487.835 ? > 385.639 ops/us > StableStaticBenchmark.dcl thrpt 10 6605.239 ? > 210.610 ops/us > StableStaticBenchmark.stable thrpt 10 14338.239 ? > 1426.874 ops/us > StableStaticBenchmark.staticCHI thrpt 10 13780.341 ? > 1839.651 ops/us > > > Performance for stable lists (thread safe) in both instance and static > contexts whereby we access a single value compared to `ArrayList` instances > (which are not thread-safe) (all threads): > > > Benchmark Mode Cnt Score > Error Units > StableListElementBenchmark.instanceArrayList thrpt 10 5812.992 ? > 1169.730 ops/us > StableListElementBenchmark.instanceList thrpt 10 4818.643 ? > 704.893 ops/us > StableListElementBenchmark.staticArrayListthrpt 10 7614.741 ? > 564.777 ops/us > StableListElementBe... Per Minborg has updated the pull request incrementally with one additional commit since the last revision: Simplify exception handling and add benchmarks - Changes: - all: https://git.openjdk.org/jdk/pull/18794/files - new: https://git.openjdk.org/jdk/pull/18794/files/2b840e06..befb2751 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk=18794=05 - incr: https://webrevs.openjdk.org/?repo=jdk=18794=04-05 Stats: 30 lines in 3 files changed: 19 ins; 6 del; 5 mod Patch: https://git.openjdk.org/jdk/pull/18794.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/18794/head:pull/18794 PR: https://git.openjdk.org/jdk/pull/18794
