RFR: 8244847: Linux/PPC: runtime/CompressedOops/CompressedClassPointers: smallHeapTest fails [v3]

[Martin Doerr]

On Tue, 1 Dec 2020 14:50:13 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

>> This is an XS sized patch to get a zerobased compressed class space on
>> Linux/PPC64 if a heap up to 2g size is configured and CDS is disabled.
>> 
>> On Linux 4.1.42 and higher we fail to get a zerobased CCS because just one
>> attempt is made to place the CCS right after the heap which will be at 4g
>> (ELF_ET_DYN_BASE) but there the java launcher is already mapped.
>> 
>> This change reuses the search already implemented for AARCH64.
>> 
>>                   Master without Fix                               Master with Fix
>> 
>> -Xmx   Narrow klass base     Compressed Class Space    Narrow klass base     Compressed Class Space
>> ----------------------------------------------------------------------------------------------------
>> 512m   0x00007fff00000000 !  0x00007fff00000000        0x0000000000000000    0x0000000200000000
>>   1g   0x00007fff14000000 !  0x00007fff14000000        0x0000000000000000    0x0000000200000000
>>   2g   0x00007fff30000000 !  0x00007fff30000000        0x0000000000000000    0x0000000200000000
>>   3g   0x0000000000000000    0x00000007c0000000        0x0000000000000000    0x00000007c0000000
>>   4g   0x0000000000000000    0x00000007c0000000        0x0000000000000000    0x00000007c0000000
>>   8g   0x0000000000000000    0x00000007c0000000        0x0000000000000000    0x00000007c0000000
>>  12g   0x0000000000000000    0x00000007c0000000        0x0000000000000000    0x00000007c0000000
>>  16g   0x0000000000000000    0x00000007c0000000        0x0000000000000000    0x00000007c0000000
>>  20g   0x0000000000000000    0x00000007c0000000        0x0000000000000000    0x00000007c0000000
>>  24g   0x0000000000000000    0x00000007c0000000        0x0000000000000000    0x00000007c0000000
>>  28g   0x0000001702000000    0x0000001702000000        0x0000001702000000    0x0000001702000000
>>  32g   0x0000000000000000    0x0000000080000000        0x0000000000000000    0x0000000080000000
>>  40g   0x0000000000000000    0x0000000080000000        0x0000000000000000    0x0000000080000000
>>  48g   0x0000000000000000    0x0000000080000000        0x0000000000000000    0x0000000080000000
>
> Richard Reingruber has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Changes based on Thomas' feedback.

Thanks for fixing it!

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

Marked as reviewed by mdoerr (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1512