RFR: JDK-8275608: runtime/Metaspace/elastic/TestMetaspaceAllocationMT2 too slow [v2]

[Aleksey Shipilev]

On Fri, 29 Oct 2021 08:31:40 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Small tweaks to make these elastic metaspace stress tests faster.
>> 
>> Before, runtime for individual tests was wobbling between 40+ seconds and some rare timeouts at 3+ minutes, depending on machine load and random luck. Now, we get a steadfast 35-37 seconds.
>> 
>> I tested this manually, checking the numbers that we really test what we want to test (a lot of arena activity). Also GHAs and SAP nightlies.
>> 
>> Thanks, Thomas
>
> Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:
> 
>   adapt copyrights

Looks fine to me, some minor nits I wondered about below.

test/hotspot/jtreg/runtime/Metaspace/elastic/MetaspaceTestManyArenasManyThreads.java line 66:

> 64: 
> 65:             for (RandomAllocatorThread t: threads) {
> 66:                 if (t.allocator.arena.numAllocationFailures > 1000) {

Feels like `numAllocationFailures` should be `volatile` (actually, `VarHandles.getOpaque` would be enough, but you probably don't want to bring all that fuss in)?

test/hotspot/jtreg/runtime/Metaspace/elastic/RandomAllocator.java line 62:

> 60:     // Allocate a random amount from the arena. If dice hits right, add this to the deallocation list.
> 61:     void allocateRandomly() {
> 62:         breatheTicks ++;

Suggestion:

        breatheTicks++;

test/hotspot/jtreg/runtime/Metaspace/elastic/RandomAllocator.java line 78:

> 76:     // Randomly choose one of the allocated in the deallocation list and deallocate it
> 77:     void deallocateRandomly() {
> 78:         breatheTicks ++;

Suggestion:

        breatheTicks++;

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

Marked as reviewed by shade (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6041