RFR: 8212995: Consider placing the Integer.IntegerCache and cached Integer objects in the closed archive heap region

[Ioi Lam]

Hi Jiangli,

static ArchivableStaticFieldInfo shareable_subgraph_entry_fields[] = {...}
static ArchivableStaticFieldInfo subgraph_entry_fields[] = {...}

Maybe these should be renamed to 
{open/closed}_archive_subgraph_entry_fields?

Also, I think we should add a strong warning about what objects can be 
placed in closed_archive_subgraph_entry_fields[]. Any references stored 
in these objects must not be modified at run time (or else we could have 
a pointer that from the closed region to the outside, violating the 
properties of the closed region.

Maybe we should also add a warning in Integer.java, something akin to 
"if you modify this class, check to see if it can still meet the 
requirements in heapShared.cpp"?

The rest of the code seems OK to me.

As a future improvement, for all the objects whose fields are all 
non-reference, final fields, maybe we can automatically put them in the 
closed archive region? For example, all archived primitive box objects 
are in this category.

Thanks
- Ioi

On 10/31/18 12:45 PM, Jiangli Zhou wrote:
> On 10/31/18 12:08 PM, Jiangli Zhou wrote:
>
>> Hi Ioi,
>>
>> Here is an updated webrev with renaming of the 'is_shared' argument. 
>> I decided to go with your suggestion, 'is_closed_archive'.
>>
>> http://cr.openjdk.java.net/~jiangli/8212995/webrev.01/
>
> BTW, in above webrev, I also included a typo fix for the following 
> warning that Mandy found (thanks Mandy!)
>
> @@ -1324,11 +1329,11 @@
>    // header data
>    const char* prop = 
> Arguments::get_property("java.system.class.loader");
>    if (prop != NULL) {
>      warning("Archived non-system classes are disabled because the "
>              "java.system.class.loader property is specified (value = 
> \"%s\"). "
> -            "To use archived non-system classes, this property must 
> be not be set", prop);
> +            "To use archived non-system classes, this property must 
> not be set", prop);
>      _has_platform_or_app_classes = false;
>    }
>
> Thanks,
> Jiangli
>>
>> Thanks,
>>
>> Jiangli
>>
>>
>> On 10/30/18 4:19 PM, Jiangli Zhou wrote:
>>> Hi Ioi,
>>>
>>> On 10/30/18 3:00 PM, Ioi Lam wrote:
>>>
>>>> Hi Jiangli,
>>>>
>>>> This looks promising.
>>>>
>>>> Now a full review yet, but I am wondering about the name of the 
>>>> is_shared parameter
>>>>
>>>>   void add_subgraph_entry_field(int static_field_offset, oop v, 
>>>> bool is_shared);
>>>>
>>>> Since this is part of "heapShared", everything is "shared" in some 
>>>> sense of the word. It could be confusing to say something is more 
>>>> shared than other things which also shared ...
>>>>
>>>> How "is_closed_archive" instead?
>>> Yes, our 'shared' has broader meaning. "is_closed_archive" or 
>>> "is_closed_space" sounds good to me. I'll rename.
>>>
>>> Thanks,
>>> Jiangli
>>>>
>>>> Thanks
>>>> - Ioi
>>>>
>>>>
>>>> On 10/30/2018 01:57 PM, Jiangli Zhou wrote:
>>>>> Please review the following change for moving the archived 
>>>>> Integer.IntegerCache and it's cached Integer objects (256) to the 
>>>>> closed archiving heap region. The IntegerCache subgraph does not 
>>>>> contain any reference that's changed at runtime (good candidate 
>>>>> for sharing). Moving the whole subgraph into the closed archive 
>>>>> heap region allows the memory to be shared by different JVM 
>>>>> instances at runtime. The saving is 4K per JVM instance running 
>>>>> the same or different java application simultaneously. Although 4K 
>>>>> is not significant, in a larger picture the saving is much bigger 
>>>>> (4k * (JVM_instance_num - 1) * host_num).
>>>>>
>>>>> As part of the change, I also restructured the code to allow us to 
>>>>> plug in more shareable subgraphs in the closed archive heap region 
>>>>> for runtime footprint saving in the future.
>>>>>
>>>>> The 'st' space is renamed to 'ca' (closed archive) space since it 
>>>>> now contains other types of objects besides j.l.Strings.
>>>>>
>>>>> webrev: http://cr.openjdk.java.net/~jiangli/8212995/webrev.00/
>>>>> RFE: https://bugs.openjdk.java.net/browse/JDK-8212995
>>>>>
>>>>> Before:
>>>>>
>>>>> mc  space:      8416 [  0.0% of total] out of     12288 bytes [ 
>>>>> 68.5% used] at 0x0000000800000000
>>>>> rw  space:   3946640 [ 21.4% of total] out of   3948544 bytes 
>>>>> [100.0% used] at 0x0000000800003000
>>>>> ro  space:   7319328 [ 39.6% of total] out of   7319552 bytes 
>>>>> [100.0% used] at 0x00000008003c7000
>>>>> md  space:      2416 [  0.0% of total] out of      4096 bytes [ 
>>>>> 59.0% used] at 0x0000000800ac2000
>>>>> od  space:   6475944 [ 35.0% of total] out of   6479872 bytes [ 
>>>>> 99.9% used] at 0x0000000800ac3000
>>>>> st0 space:    438272 [  2.4% of total] out of    438272 bytes 
>>>>> [100.0% used] at 0x00000007ffc00000 <<<<<<<<<<
>>>>> oa0 space:    282624 [  1.5% of total] out of    282624 bytes 
>>>>> [100.0% used] at 0x00000007ff800000 <<<<<<<<<<
>>>>> total    :  18473640 [100.0% of total] out of  18485248 bytes [ 
>>>>> 99.9% used]
>>>>>
>>>>> After:
>>>>>
>>>>> mc  space:      8416 [  0.0% of total] out of     12288 bytes [ 
>>>>> 68.5% used] at 0x0000000800000000
>>>>> rw  space:   3946640 [ 21.4% of total] out of   3948544 bytes 
>>>>> [100.0% used] at 0x0000000800003000
>>>>> ro  space:   7319304 [ 39.6% of total] out of   7319552 bytes 
>>>>> [100.0% used] at 0x00000008003c7000
>>>>> md  space:      2416 [  0.0% of total] out of      4096 bytes [ 
>>>>> 59.0% used] at 0x0000000800ac2000
>>>>> od  space:   6475920 [ 35.0% of total] out of   6479872 bytes [ 
>>>>> 99.9% used] at 0x0000000800ac3000
>>>>> ca0 space:    442368 [  2.4% of total] out of    442368 bytes 
>>>>> [100.0% used] at 0x00000007ffc00000 <<<<<<<<<<
>>>>> oa0 space:    278528 [  1.5% of total] out of    278528 bytes 
>>>>> [100.0% used] at 0x00000007ff800000 <<<<<<<<<<
>>>>> total    :  18473592 [100.0% of total] out of  18485248 bytes [ 
>>>>> 99.9% used]
>>>>>
>>>>> Tested with appcds tests on linux-x64 locally. Running tier1-teir4 
>>>>> tests.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Jiangli
>>>>>
>>>>>
>>>>
>>>
>>
>