Hi all,
could I get reviews please for this small enhancement:
rfe: https://bugs.openjdk.java.net/browse/JDK-8221925
cr:
http://cr.openjdk.java.net/~stuefe/webrevs/8221925-metaspace-histogram/webrev.00/webrev/index.html
This patch adds a small feature to the VM.metaspace command, a size
histogram. That one is useful to get an idea of the size distribution of
allocations, as a base for improving chunk allocation strategies.
----------------
Example output:
$ jcmd stuefe VM.metaspace histo
12835:
<snip>
Size histogram:
Non-Class:
<16 <32 <64 <128 <256 <512 <1k
<2k <4k <8k <16k <32k <64k <128k <256k larger
-- by object type: --
Class 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
Symbol 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
TypeArrayU1 0 4056 2281 1098 1068 251 116
40 10 1 0 0 0 0 0 0
TypeArrayU2 2609 1698 1604 732 321 102 41
11 2 0 0 0 0 0 0 0
TypeArrayU4 78 193 49 0 0 0 0
0 0 0 0 0 0 0 0 0
TypeArrayU8 0 3563 2307 2298 1233 267 113
27 2 0 0 0 0 0 0 0
TypeArrayOther 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
Method 0 0 0 32151 0 0 0
0 0 0 0 0 0 0 0 0
ConstMethod 0 0 1225 18968 9242 1958 526
202 23 4 1 2 0 0 0 0
MethodData 0 0 0 0 0 424 2323
364 103 26 8 1 0 0 0 0
ConstantPool 0 0 0 89 286 1577 1297
450 225 110 40 10 1 0 0 0
ConstantPoolCache 0 0 187 223 344 1432 936
229 145 60 23 4 1 0 0 0
Annotations 0 0 67 0 0 0 0
0 0 0 0 0 0 0 0 0
MethodCounters 0 0 0 12838 0 0 0
0 0 0 0 0 0 0 0 0
-- by space type: --
Standard 489 4008 3222 25473 4066 1458 2239
743 227 87 44 15 2 0 0 0
Boot 539 3380 2992 33203 5796 2351 2065
580 283 114 28 2 0 0 0 0
UnsafeAnonymous 159 622 506 1221 132 202 48
0 0 0 0 0 0 0 0 0
Reflection 1500 1500 1000 8500 2500 2000 1000
0 0 0 0 0 0 0 0 0
-- total: --
2687 9510 7720 68397 12494 6011 5352
1323 510 201 72 17 2 0 0 0
Class:
<16 <32 <64 <128 <256 <512 <1k
<2k <4k <8k <16k <32k <64k <128k <256k larger
-- by object type: --
Class 0 0 0 0 0 0 4013
219 4 0 0 0 0 0 0 0
Symbol 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
TypeArrayU1 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
TypeArrayU2 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
TypeArrayU4 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
TypeArrayU8 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
TypeArrayOther 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
Method 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
ConstMethod 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
MethodData 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
ConstantPool 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
ConstantPoolCache 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
Annotations 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
MethodCounters 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
-- by space type: --
Standard 0 0 0 0 0 0 1129
143 4 0 0 0 0 0 0 0
Boot 0 0 0 0 0 0 1200
76 0 0 0 0 0 0 0 0
UnsafeAnonymous 0 0 0 0 0 0 184
0 0 0 0 0 0 0 0 0
Reflection 0 0 0 0 0 0 1500
0 0 0 0 0 0 0 0 0
-- total: --
0 0 0 0 0 0 4013
219 4 0 0 0 0 0 0 0
--------------------------
I kept the coding as simple and lean as possible. I think the patch is
reasonably small.
I ran all jtreg Metaspace tests locally; will run the usual jdk-submit
tests and put this through our nightlies at SAP.
Thank you!
Best Regards, Thomas