RFR: JDK-8232069: Enable CDS even when UseCompressedClassPointers and/or UseCompressedOops are false

[Yumin Qi]

Hi, Ioi and all


   Forget to mention tests: hs-tier1 - 4 passed.


Thanks

Yumin

On 2/6/20 2:04 PM, Yumin Qi wrote:
> Hi, Ioi
>
>
>   Thanks for the review. See answers embedded.
>
>    New URL: http://cr.openjdk.java.net/~minqi/8232069/webrev-01/
>
> On 2/5/20 10:34 AM, Ioi Lam wrote:
>> Hi Yumin,
>>
>>
>> Looks good. Some nitpicks on the tests:
>>
>> CommandLineFlagComboNegative.java: the following line is not needed.
>>
>> import jdk.test.lib.cds.CDSTestUtils.Result;
>>
> Removed.
>>
>> TestCombinedCompressedFlags.java: DUMP_NORMAL_MSG doesn't seem to be 
>> used by the test.
>>
> Removed.
>
> Also changed to use TestCommon.dump/TestCommon.exec which better to 
> check dum/run results.
>
>> DifferentHeapSizes.java: after your change, 
>> CDSTestUtils.MSG_COMPRESSION_MUST_BE_USED is no longer used anywhere 
>> in the tests. Also, This message is no longer printed by the VM. I 
>> think the CDSTestUtils.MSG_COMPRESSION_MUST_BE_USED field should be 
>> removed.
>>
>>
> Removed.
>> IncompatibleOptions.java: COOPS_DUMP_WARNING can be removed.
>>
> Removed.
>> The check_shared parameter for testExec() should be removed. It's 
>> currently used only when expectedToFail == false. However, in all the 
>> cases where expectedToFail == false, check_shared is always true.
>>
>>
> Removed.
>
>> Also, in filemap.cpp, before checking "compressed_oops() != 
>> UseCompressedOops ...", I think it will be good to add a log to print 
>> out the expected compressed mode. That way if the user gets an error, 
>> they can run with -Xlog:cds to find out exactly what the reason is. E.g.
>>
>>     log_info(cds)("Archive was created with UseCompressedOops = %d, 
>> UseCompressedClassPointers = %d",
>>                           compressed_oops(), 
>> compressed_class_pointers());
>>     if (compressed_oops() != UseCompressedOops ...
>>
> Added.
>
>
> Thanks
>
> Yumin
>
>>
>> On 2/4/20 6:01 PM, Yumin Qi wrote:
>>> Hi,
>>>
>>>    Please review fix:
>>>
>>>    Bug: https://bugs.openjdk.java.net/browse/JDK-8232069
>>>
>>>    Webrev:http://cr.openjdk.java.net/~minqi/8232069/webrev/
>>>
>>>     Description: Currently CDS only works when using compressed Oops 
>>> turned on, -XX:+UseCompressedOops (default), the fix is allowing CDS 
>>> works with uncompressed oops and uncompressed class pointers. The 
>>> contents of InstanceKlass::_fields are depending on 
>>> UseCompressedOops and UseCompressedClassPointers on/off. There are 
>>> three suggestions as described in bug description:
>>>
>>> 1. Remember the compression mode at CDS dump time. At runtime, 
>>> disable CDS if the compression mode is changed.
>>> 2. Same as 1, but save more than one CDS archives in the JDK image. 
>>> Choose the appropriate one at start-up
>>> 3. Recompute re-compute InstanceKlass::_fields at runtime.
>>>
>>> The fix takes the first one, storing UseCompressedOops and 
>>> UseCompressedClassPointers in shared archive. CDS is only allowed at 
>>> runtime if the flags are consistent with the stored versions in 
>>> archive.
>>>
>>>  Testing: hs-tier1-2
>>>
>>>
>>>   Thanks
>>>
>>>   Yumin
>>>
>>