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

Jiangli Zhou jiangli.zhou at oracle.com
Tue Oct 30 20:57:31 UTC 2018

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

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