RFR: 8255959: Timeouts in VectorConversion tests

[Martin Doerr]

On Thu, 5 Nov 2020 20:25:44 GMT, Paul Sandoz <psandoz at openjdk.org> wrote:

>> We observed many timeouts in the following test/jdk/jdk/incubator/vector tests:
>> Vector128ConversionTests.java
>> Vector256ConversionTests.java
>> Vector512ConversionTests.java
>> Vector64ConversionTests.java
>> VectorMaxConversionTests.java
>> Some machines don't support vector instructions or fewer of them and C2 uses slower alternatives.
>> 
>> Maybe there are options to make the tests faster, but I just propose to use a larger timeout value for now.
>
> I have not observed such timeouts in our test infrastructure, but was wondering if this may cause such issues. Perhaps PPC does not support the conversion intrinsics?
> 
> The timeout value is quite high, 1800 (i cannot recall what the default is). Ideally we should split this test per species. I regret that this test is not produced from a template.
> 
> Would you mind first if we can try a quick experiment to reduce the time taken? In `AbstractVectorConversionTest` there is a loop using an upper bound of `INVOC_COUNT`, perhaps if any of the species input to the relevant methods have a length > the length of the corresponding preferred species, then we can reduce the loop count.

At the moment, neither PPC nor s390 support any conversion intrinsics. Modern s390 (or 
z/Architecture to be more precise) machines have vector instructions, but nobody implemented them in hotspot. So s390 uses the regular 8 Byte registers for vectors. PPC only uses 16 Byte vectors on modern hardware (8 Byte on older hardware).

Default timeout is 1200 and I found out that 50% more makes the tests happy on all our machines.

We could do an experiment, but I'm not familiar with the test.

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

PR: https://git.openjdk.java.net/jdk/pull/1079