RFR(xs): 8247252: TestCombinedCompressedFlags.java failed src/hotspot/share/services/virtualMemoryTracker.cpp:388 Error: ShouldNotReachHere()

[Yumin Qi]

Hi, Thomas


   Ignore my comment --- use_requested_addr is not address. Sorry for 
this. BTW, I don't think you should change test cases to add NMT 
tracking, that will give too much information on output. I agree with 
Calvin you can always using vmoptions + group selection on jtreg for 
testing your change.


Thanks

Yumin

On 6/10/20 10:11 AM, Yumin Qi wrote:
> Hi, Thomas
>
> Â Â  I verified your patch, it looks good to me. One minor comment:
>
> 2271     result = MAP_ARCHIVE_MMAP_FAILURE;
> 2272 log_debug(cds)("Failed to reserve spaces 
> (use_requested_addr=%u)", (unsigned)use_requested_addr); It is not 
> intuitive for an address printed as unsigned, could you using 
> PTR_FORMAT? Thanks Yumin
>
> On 6/10/20 6:09 AM, Thomas Stüfe wrote:
>> Hi all,
>>
>> could I please have reviews for this bug fix.
>>
>> JBS: https://bugs.openjdk.java.net/browse/JDK-8247252
>> webrev:
>> http://cr.openjdk.java.net/~stuefe/webrevs/8247252-cds-nmt-ccps-off/webrev.00/webrev/ 
>>
>>
>> This bug was introduced with "8243535 NMT may show wrong numbers for CDS
>> and CCS".
>>
>> The error is that a VM loading a shared archive but having compressed 
>> class
>> pointers disabled would reserve space for the CDS but fail to 
>> register it
>> with the correct tag with NMT. So, inside NMT it still is marked as
>> "mtUnknown". This leads to a follow up error when the actual archive 
>> files
>> are to be mapped into this reserved region, since the region is 
>> expected to
>> carry the "mtClassShared" tag for this to work.
>>
>> The fix is simple to add the missing registration in metaspaceShared.cpp
>> when the cds has been reserved for the non-class-space case:
>>
>> @@ -2469,10 +2470,12 @@
>>       archive_space_rs = ReservedSpace(archive_space_size,
>> archive_space_alignment,
>>                                        false /* bool large */,
>> (char*)base_address);
>>       if (archive_space_rs.is_reserved()) {
>>         assert(base_address == NULL ||
>>                (address)archive_space_rs.base() == base_address, 
>> "Sanity");
>> +      // Register archive space with NMT.
>> + MemTracker::record_virtual_memory_type(archive_space_rs.base(),
>> mtClassShared);
>>         return archive_space_rs.base();
>>       }
>>       return NULL;
>>     }
>>
>> All the rest is fluff:
>>
>> - added logging in a number of places to make analysis of these kinds of
>> errors simpler
>> - explicitly switched on NMT for a number of cds jtreg tests.
>>
>> ---
>>
>> The reason we did not see these errors before in our (SAPs) CI was 
>> that we
>> run our tests with NMT (by default) switched off. Apparently Oracle runs
>> the jtreg tests with NMT enabled via -vmoptions? We will change our 
>> CI to
>> do this too. But it would be good if the test flags would be published
>> somewhere, and we would all use the same flags.
>>
>> Thanks, Thomas