RFR: 8239423: [TESTBUG] jdk/jfr/jvm/TestJFRIntrinsic.java failed with -XX:-TieredCompilation

[David Holmes]

On 19/02/2020 5:40 pm, David Holmes wrote:
> On 19/02/2020 5:26 pm, Ao Qi wrote:
>> On Wed, Feb 19, 2020 at 3:01 PM David Holmes <david.holmes at oracle.com> 
>> wrote:
>>>
>>> Hi,
>>>
>>> On 19/02/2020 4:20 pm, Ao Qi wrote:
>>>> Hi all,
>>>>
>>>> Could you please review this patch?
>>>>
>>>> JBS: https://bugs.openjdk.java.net/browse/JDK-8239423
>>>> webrev: http://cr.openjdk.java.net/~aoqi/8239423/webrev.00/ (22 lines
>>>> changed: 19 ins; 0 del; 3 mod; 153 unchg)
>>>
>>> I'm not seeing the connection between the reported bug and the fix. It
>>> seems to me that passing -XX:-TieredCompilation to a test that
>>> explicitly sets -XX:TieredStopAtLevel=n is simply not something that can
>>> work. In fact I'm surprised it doesn't trigger an error when validating
>>> the command-line args.
>>
>> "-XX:-TieredCompilation" in the title is a way to trigger the bug, not
>> the cause. Sorry for the confusion. The bug also can be triggered by
>> the jdk configured with --with-jvm-features=-compiler1.
>>
>>>
>>> You fix seems more related to whether C1 and/or C2 are available.
>>
>> Yes.
> 
> I've had a look at this and I'm seeing the problem but I don't yet think 
> this is the right fix. I see some general issues with the ability to use 
> the compiler flags in a way that may not make sense (to me anyway); then 
> I see an issue with the way the test determines the available levels.
> 
> Looking at the test it determines the available levels as follows:
> - If tiered is enabled
>      - use TieredStopAtLevel=n to set the maximum level and thus the 
> available levels
> - else if server
>    - only level is 4
> - else // client, minimal, emulated client
>    - only level is 1
> 
> So with -TieredCompilation or a server only build the level is set to 4. 
> But the WhiteBox::compile_method rejects that as an invalid level for 
> the configuration.
> 
> I don't think the fix is to require C2, in fact I don't see how that 
> fixes the problem anyway if you have a C2 only build without tiered 
> because the test will still use level=4 which the WB rejects:
> 
> STDOUT:
> WB error: invalid compilation level 4
> 
> The test in WB is:
> 
>    if (comp_level > MIN2((CompLevel) TieredStopAtLevel, 
> CompLevel_highest_tier))
> 
> but I don't know how either of those values are set when (a) tiered is 
> disabled; or (b) you have a C1 or C2 only build (which should imply 
> tiered is disabled as well).

Digging deeper if C2 exists then CompLevel_highest_tier should be set as:

#if defined(COMPILER2)
CompLevel  CompLevel_highest_tier      = CompLevel_full_optimization;

where:

CompLevel_full_optimization = 4

and from the command-line:

-XX:TieredStopAtLevel=4

and so I don't understand how the above failure can trigger. One of 
those fields must not be what is is expected to be.

David


> Cheers,
> David
> 
>> Cheers,
>> Ao Qi
>>
>>>
>>> ??
>>>
>>> Cheers,
>>> David
>>>
>>>> Thanks,
>>>> Ao Qi
>>>>
>>