RFR JDK-8059510 Compact symbol table layout inside shared archive

[Jiangli Zhou]

Hi Staffan,

Here is updated webrev: 
http://cr.openjdk.java.net/~jiangli/8059510/webrev.05/. The permission 
changes for the new commands are in 
http://cr.openjdk.java.net/~jiangli/8059510/webrev.05/src/share/vm/classfile/compactHashtable.hpp.html.

Thanks,
Jiangli

On 10/28/2014 09:34 AM, Jiangli Zhou wrote:
> That's good to know! Thanks, Staffan. I'll set the permission for the 
> new commands.
>
> Thanks,
> Jiangli
>
> On 10/28/2014 12:11 AM, Staffan Larsen wrote:
>> Thanks for doing these changes!
>>
>> I see one more thing that is missing from the Diagnostic Commands. 
>> Because these commands can potentially expose sensitive data, they 
>> should be protected from remote execution by anyone. Only 
>> authenticated users with the correct permissions should be able to 
>> run them. To achieve that, you simply have to override the 
>> permission() method in Dcmd like this:
>>
>>    static const JavaPermission permission() {
>>      JavaPermission p = {"java.lang.management.ManagementPermission",
>>                          "monitor", NULL};
>>      return p;
>>    }
>>
>> Thanks,
>> /Staffan
>>
>> On 28 okt 2014, at 01:21, Jiangli Zhou <jiangli.zhou at oracle.com> wrote:
>>
>>> Hi Staffan,
>>>
>>> I moved the symboltable/stringtable dumping implementations to 
>>> symbolTable.cpp and stringTable.cpp. The SymboltableDCmd and 
>>> StringtableDCmd class definitions are placed in the new 
>>> compactHashTable.hpp. I also removed the 
>>> -XX:+UnlockDiagnosticVMOptions requirement for the VM.symboltable 
>>> and VM.stringtable options based on our separate discussion.
>>>
>>> http://cr.openjdk.java.net/~jiangli/8059510/webrev.04/
>>>
>>> Thanks for the suggestions,
>>>
>>> Jiangli
>>>
>>> On 10/23/2014 09:45 AM, Jiangli Zhou wrote:
>>>> Hi Staffan,
>>>>
>>>> No problem, the review request is still open. :) Thanks for the 
>>>> suggestion. I'll try to incorporate it.
>>>>
>>>> Thanks!
>>>> Jiangli
>>>>
>>>> On 10/22/2014 11:15 PM, Staffan Larsen wrote:
>>>>> Jiangli,
>>>>>
>>>>> Sorry for being late to the review. I would suggest moving the 
>>>>> diagnostic command implementation from diagnosticCommand.cpp/hpp 
>>>>> to symbolTable.cpp/hpp. If all dcmds are implemented in 
>>>>> diagnosticCommand.cpp, then that file will grow to become quite 
>>>>> large, so I would prefer having the commands close to the code 
>>>>> they interact with (there are probably a couple more that should 
>>>>> be moved). The only problem you may run into is to find a good 
>>>>> place to call DCmdFactory::register_DCmdFactory(), but that can be 
>>>>> done anywhere during the initialization of the VM.
>>>>>
>>>>> Thanks,
>>>>> /Staffan
>>>>>
>>>>>
>>>>> On 22 okt 2014, at 02:09, Jiangli Zhou <jiangli.zhou at oracle.com> 
>>>>> wrote:
>>>>>
>>>>>> Hi Gerard,
>>>>>>
>>>>>> Please see the updated webrev: 
>>>>>> http://cr.openjdk.java.net/~jiangli/8059510/webrev.03/.
>>>>>>
>>>>>> Thanks,
>>>>>> Jiangli
>>>>>>
>>>>>> On 10/21/2014 02:57 PM, Jiangli Zhou wrote:
>>>>>>> Hi Gerard,
>>>>>>>
>>>>>>> On 10/21/2014 02:32 PM, Gerard Ziemski wrote:
>>>>>>>> On 10/21/2014 1:45 PM, Jiangli Zhou wrote:
>>>>>>>>> There are pros and cons for both dynamically and statically 
>>>>>>>>> allocating the _shared_table. Dynamically allocating the 
>>>>>>>>> _shared_table as you suggested adds overhead of the memory 
>>>>>>>>> allocation and the overhead of the extra NULL check when the 
>>>>>>>>> _shared_table is in use. When doing optimization, we try to 
>>>>>>>>> have the least overhead for the fast case, so we could make 
>>>>>>>>> the fast case faster (that's when CDS is used).
>>>>>>>>>
>>>>>>>>> Maybe we could make _shared_table.lookup() inlined and reduce 
>>>>>>>>> the overhead of the function call when CDS is not used.
>>>>>>>> I think that would be OK, though it will require a reader of 
>>>>>>>> the code to follow the call through to find out it's cheap NOP 
>>>>>>>> when CDS is off, unless we add a nice comment here?
>>>>>>> I'll add some comments. Thanks for the suggestion.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Jiangli
>>>>>>>
>>>>>>>> cheers
>>>>>>>>
>