RFR: 8062537: [TESTBUG] Conflicting GC combinations in hotspot tests

Bengt Rutisson bengt.rutisson at oracle.com
Tue Nov 4 08:40:43 UTC 2014


Hi Dima,

Thanks for the answers. I think the currently proposed patch is a good 
start. We will have to evolve the @requires tag in the future, but let's 
have that discussion separate from this review. And we can start that 
discussion later when we have more experience with the current version 
of @requires.

Thanks for doing this!
Bengt



On 11/3/14 10:12 PM, Dmitry Fazunenko wrote:
> Hi Bengt,
>
> That's great that we have very closed visions!
>
> The general comment: currently, jtreg doesn't support any sort of 
> plugins, so you can't provide a VM specific handler of the @requires 
> or another tag. This is very annoying limitation and we have to live 
> with it.
>
> A few more comments inline.
>
>
> On 03.11.2014 16:31, Bengt Rutisson wrote:
>>
>>
>> Hi Dima,
>>
>> Answers inline.
>>
>> On 10/31/14 1:56 PM, Dmitry Fazunenko wrote:
>>> Hi Bengt,
>>>
>>> Thanks a lot for your detailed feedback, we appreciate it very much!
>>>
>>> See comments inline.
>>>
>>> On 31.10.2014 1:09, Bengt Rutisson wrote:
>>>>
>>>> Hi Evgeniya,
>>>>
>>>> On 10/30/14 3:05 PM, Evgeniya Stepanova wrote:
>>>>> Hi,
>>>>>
>>>>> Please review changes for 8062537, the OpenJDK/hotspot part of the 
>>>>> JDK-8019361 <https://bugs.openjdk.java.net/browse/JDK-8019361>
>>>>>
>>>>> bug: https://bugs.openjdk.java.net/browse/JDK-8062537
>>>>> fix: http://cr.openjdk.java.net/~eistepan/8062537/webrev.00/
>>>>>
>>>>> Problem: Some tests explicitly set GC and fail when jtreg set 
>>>>> another GC.
>>>>> Solution: Such tests marked with the jtreg tag "requires" to skip 
>>>>> test if there is a conflict
>>>>
>>>> Thanks for fixing this! It is really great that we finally start 
>>>> sorting this out.
>>>>
>>>> First a general comment. The @requires tag has been developed 
>>>> without much cooperation with the GC team. We did have a lot of 
>>>> feedback when it was first presented a year ago, but it does not 
>>>> seem like this feedback was incorporated into the @requires that 
>>>> was eventually built.
>>>
>>> We tried to implement as much developer's wishes as possible. But 
>>> not everything is possible, sorry for that.
>>
>> Yes, I'm sure you have done your best. It's just that we have been 
>> requesting this feature for 3 years and I was expecting us to be able 
>> to influence the feature much more than was the case now.
>
> My personal hope: @requires will address ~90% of existing issues.
>
>>
>>>
>>>>
>>>> I think this change that gets proposed now is a big step forward 
>>>> and I won't object to it. But I am pretty convinced that we will 
>>>> soon run in to the limitations of the current @requires 
>>>> implementation and we will have to redo this work.
>>>>
>>>> Some of the points I don't really like about the @requires tag are:
>>>>
>>>> - the "vm.gc" abstraction is more limiting than helping. It would 
>>>> have been better to just "require" any command line flag.
>>> "vm.gc" is an alias to a very popular flag. It's also possible to use:
>>> vm.opt.UseG1GC == true instead.
>>>
>>> The table with all vars available in jtreg:
>>> http://jre.us.oracle.com/java/re/jtreg/4.1/promoted/latest/binaries/jtreg/doc/jtreg/tag-spec.html#requires_names
>>
>> The problem with having this matching built in to JTreg is that it 
>> makes it very hard to change. When we discussed this a year ago I 
>> think we said that JTreg should only provide a means to test against 
>> the command line and a hook for running some java code in the 
>> @requires tag. That way we could put logic like this in a test 
>> library that is under our control. This would make it easy for us to 
>> change and also enables us to use different logic for different versions.
>
> I would be glad to have own harness...
>
>>
>>>
>>>> - the requirement should be per @run tag. Right now we have to do 
>>>> what you did in this change and use vm.gc=null even when some tests 
>>>> could actually have been run when a GC was specified.
>>> it would be great, but it will unlikely happen in jtreg, as well as 
>>> test case support.
>>
>> what do you mean with test case support? Hi Evgeniya,
>
> Under test case support I mean ability to treat each @run as a 
> separate test. Now
>
> @test
> @run -XX:g1RegSize=1m MyTest
> @run -XX:g1RegSize=2m MyTest
> @run -XX:g1RegSize=4m MyTest
> class MyTest {
> }
>
> is always a single test. You can't exclude, or re-run a part of it.
>
>
>>
>>>
>>>> - there are many tests that require more than just a specific GC. 
>>>> Often there are other flags that can't be changed either for the 
>>>> test to work properly.
>>>
>>> yes. conflicting GC is just the most popular problem caused by 
>>> conflicting options.
>>> If we address this issue and we are satisfied with solution, we 
>>> could move further.
>>
>> Yes, I agree that taking one step at the time is good. Personally I 
>> would have preferred that the first step was a "just run the command 
>> line as specified in the @run tag" step.
>>
>>>
>>>>
>>>> Maybe this is not the right place to discuss the current 
>>>> implementation of the @requires tag. I just want to say that I'm 
>>>> not too happy about how the @requires tag turned out. But assuming 
>>>> we have to use it the way it is now I guess the proposed changeset 
>>>> looks good.
>>>
>>> yes, this thread is about change made by Evgeniya, not about jtreg :)
>>> And thanks for reviewing it!
>>
>> Agreed. And as I said, I think the patch looks ok. I have not looked 
>> at all tests. But if they now pass with the combinations that we test 
>> with I guess they should be ok.
>
> Excellent! Thanks a lot!
>
>>
>>>
>>>>
>>>>> Tested locally with different GC flags (-XX:+UseG1GC, 
>>>>> -XX:+UseParallelGC, -XX:+UseSerialGC, -XX:+UseConcMarkSweep and 
>>>>> without any GC flag). Tests are being excluded as expected. No 
>>>>> tests failed because of the conflict.
>>>> Have you tested with -Xconcgc too? It's an alias for 
>>>> -XX:+UseConcMarkSweepGC.
>>>
>>> '-Xconcgc' is not supported yet. (bug in jtreg, I will submit)
>>
>> Ok. Thanks.
>>
>>>
>>>>
>>>> I think some of the test, like 
>>>> test/gc/startup_warnings/TestDefNewCMS.java, will fail if you run 
>>>> with -XX:+UseParNewGC. Others, like 
>>>> test/gc/startup_warnings/TestParNewCMS.java, will fail if you run 
>>>> with -XX:-UseParNewGC. Could you test these two cases too?
>>>
>>> These two tests ignore vm flags.
>>> Add @requires here is not necessary, but it will allow not execute 
>>> the tests when not needed.
>>> So, if we run HS tests with 4 GC, we don't need to run these tests 4 
>>> times, 1 should be enough.
>>
>> Do we really want to use the @requires functionality for this 
>> purpose? It seems like a way of misusing @requires. If we just want 
>> the tests to be run once I think Leonid's approach with tests lists 
>> seems more suitable.
>
> No, it's not a purpose of course, it's just side effect :)
>
>
>> But are you sure that this is the reason for the @requires in this 
>> case? TestDefNewCMS does sound like a test that is DefNew specific. I 
>> don't see a reason to run it with ParNew. If it doesn't fail today it 
>> should probably be changed so that it does fail if it is run with the 
>> wrong GC.
>
> @requires - is not the silver bullet, but it's quite easy way to solve 
> a lot of issues.
>
> I hope, @requires will allow to reduce the number of "selfish" tests, 
> which produce a new java process to ignore vm flags coming from 
> outside. No @requires, no other mechanism could 100% protect a test 
> from running with conflicting options, but this is not the goal.
>
> If one runs tests with an exotic option, like a new G2 collector, 
> there shouldn't mass failures caused by options conflicts. But a few 
> failures could be handled manually.
>
>
>>
>>>
>>>> Similarly it looks to me like there are tests that will fail if you 
>>>> run them with -XX:-UseParallelOldGC or -XX:+UseParallelOldGC.
>>>>
>>>> Just a heads up. These two tests will soon be removed. I'm about to 
>>>> push a changeset that removes them:
>>>>
>>>> test/gc/startup_warnings/TestCMSIncrementalMode.java
>>>> test/gc/startup_warnings/TestCMSNoIncrementalMode.java
>>> okay, thank for letting us know.
>>>
>>>>
>>>> Is there some way of making sure that all tests are run at one time 
>>>> or another. With this change there is a risk that some tests are 
>>>> never run and always skipped. Will we somehow be tracking what gets 
>>>> skipped and make sure that all tests are at least run once with the 
>>>> correct GC so that it is not skipped all the time?
>>>
>>> This is a very good question!
>>> jtreg now doesn't report skipped tests, hopefully it will do soon, 
>>> after getting fix of:
>>> https://bugs.openjdk.java.net/browse/CODETOOLS-7900934
>>>
>>> And yes, tracking tests which are not run is important thing.
>>> @requires - is not the only to exclude test from execution.
>>>
>>> Other examples:
>>>
>>> /*
>>>   *@ignore
>>>   *@test
>>>   */
>>> ...
>>>
>>> /*@bug 4445555
>>>   *@test
>>>   */
>>> ...
>>> Such tests will never be run, because jtreg treats as test only 
>>> files with @test on the first place...
>>>
>>> So,  making sure that tests do not disappear is important SQE task, 
>>> we know about that, we're thinking on solution (may be very 
>>> actively).  But this subject for another discussion, not within RFR :)
>>
>> Right. Glad to hear that you are actively working on this!
>
> I was going to say "not very actively", but never mind, we know about 
> this problem. With introducing @requires mechanism it will become more 
> important!
>
>
> Thanks for your comments!
>
> -- Dima
>
>
>>
>> Bengt
>>
>>>
>>> Thanks,
>>> Dima
>>>
>>>
>>>
>>>>
>>>> Thanks,
>>>> Bengt
>>>>
>>>>>
>>>>> Thanks,
>>>>> Evgeniya Stepanova
>>>>>
>>>>
>>>
>>
>

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