> UUID is the very important class that is used to track identities of objects
> in large scale systems. On some of our systems, `UUID.randomUUID` takes >1%
> of total CPU time, and is frequently a scalability bottleneck due to
> `SecureRandom` synchronization.
>
> The major issue with UUID code itself is that it reads from the single
> `SecureRandom` instance by 16 bytes. So the heavily contended `SecureRandom`
> is bashed with very small requests. This also has a chilling effect on other
> users of `SecureRandom`, when there is a heavy UUID generation traffic.
>
> We can improve this by doing the bulk reads from the backing SecureRandom and
> possibly striping the reads across many instances of it.
>
>
> Benchmark Mode Cnt Score Error Units
>
> ### AArch64 (m6g.4xlarge, Graviton, 16 cores)
>
> # Before
> UUIDRandomBench.single thrpt 15 3.545 ± 0.058 ops/us
> UUIDRandomBench.max thrpt 15 1.832 ± 0.059 ops/us ; negative scaling
>
> # After
> UUIDRandomBench.single thrpt 15 4.823 ± 0.023 ops/us
> UUIDRandomBench.max thrpt 15 6.561 ± 0.054 ops/us ; positive scaling,
> ~1.5x
>
> ### x86_64 (c6.8xlarge, Xeon, 18 cores)
>
> # Before
> UUIDRandomBench.single thrpt 15 2.710 ± 0.038 ops/us
> UUIDRandomBench.max thrpt 15 1.880 ± 0.029 ops/us ; negative scaling
>
> # After
> Benchmark Mode Cnt Score Error Units
> UUIDRandomBench.single thrpt 15 3.109 ± 0.026 ops/us
> UUIDRandomBench.max thrpt 15 3.561 ± 0.071 ops/us ; positive
> scaling, ~1.2x
>
>
> Note that there is still a scalability bottleneck in current default random
> (`NativePRNG`), because it synchronizes over a singleton instance for SHA1
> mixer, then the engine itself, etc. -- it is quite a whack-a-mole to figure
> out the synchronization story there. The scalability fix in current default
> `SecureRandom` would be much more intrusive and risky, since it would change
> a core crypto class with unknown bug fanout.
>
> Using the bulk reads even when the underlying PRNG is heavily synchronized is
> still a win. A more scalable PRNG would benefit from this as well. This PR
> adds a system property to select the PRNG implementation, and there we can
> clearly see the benefit with more scalable PRNG sources:
>
>
> Benchmark Mode Cnt Score Error Units
>
> ### x86_64 (c6.8xlarge, Xeon, 18 cores)
>
> # Before, hacked `new SecureRandom()` to
> `SecureRandom.getInstance("SHA1PRNG")`
> UUIDRandomBench.single thrpt 15 3.661 ± 0.008 ops/us
> UUIDRandomBench...
Aleksey Shipilev has updated the pull request with a new target base due to a
merge or a rebase. The pull request now contains 13 commits:
- Revert test changes
- Merge branch 'master' into JDK-8308804-uuid-buffers
- Simplify clinit
- Remove the properties
- Swap lsb/msb
- Fine-tune exceptions
- Handle privileged properties
- Use ByteArray to convert. Do version/variant preparations straight on
locals. Move init out of optimistic lock section.
- More touchups
- Comment updates
- ... and 3 more: https://git.openjdk.org/jdk/compare/4460429d...fd7eaa1a
-------------
Changes: https://git.openjdk.org/jdk/pull/14135/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14135&range=06
Stats: 197 lines in 2 files changed: 186 ins; 8 del; 3 mod
Patch: https://git.openjdk.org/jdk/pull/14135.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/14135/head:pull/14135
PR: https://git.openjdk.org/jdk/pull/14135
