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

[Ioi Lam]

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?

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
>
>