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

[Jiangli Zhou]

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