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Created March 27, 2018 05:55
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Java10 の App CDS を使ってみたけど、効果が出なかったケース
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app-cds.md

Java10 に Class Data Sharing なる機能が追加されたので試したけど、テストケースが良くない場合の話。

サンプル

Spring Boot の maven プロジェクト

実行手順

(1) JVM オプションを指定して mvn コマンドを実行してクラスリストを出力する

$ export MAVEN_OPTS="-XX:+UnlockCommercialFeatures -Xshare:off -XX:DumpLoadedClassList=hello.classlist -XX:+UseAppCDS"

$ ./mvnw validate
/Users/smochida/tmp/app-cds-sample/j10
skip writing class com/sun/proxy/$Proxy0 from source __JVM_DefineClass__ to classlist file
skip writing class com/sun/proxy/$Proxy1 from source __JVM_DefineClass__ to classlist file
skip writing class com/sun/proxy/$Proxy2 from source __JVM_DefineClass__ to classlist file
skip writing class com/sun/proxy/$Proxy11 from source __JVM_DefineClass__ to classlist file
skip writing class com/sun/proxy/$Proxy13 from source __JVM_DefineClass__ to classlist file
[INFO] Scanning for projects...
[INFO] 
[INFO] ---------------------< com.example:app-cds-sample >---------------------
[INFO] Building demo 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.951 s
[INFO] Finished at: 2018-03-27T14:36:02+09:00
[INFO] ------------------------------------------------------------------------

$ ll
total 144
drwxr-xr-x  9 smochida  staff    288  3 27 14:35 .
drwxr-xr-x  4 smochida  staff    128  3 27 14:13 ..
-rw-r--r--  1 smochida  staff    261  3 27 14:30 .gitignore
drwxr-xr-x  3 smochida  staff     96  3 27 14:30 .mvn
-rw-r--r--  1 smochida  staff  49005  3 27 14:36 hello.classlist
-rwxr-xr-x  1 smochida  staff   6468  3 27 14:30 mvnw
-rw-r--r--  1 smochida  staff   4994  3 27 14:30 mvnw.cmd
-rw-r--r--  1 smochida  staff   2744  3 27 14:30 pom.xml
drwxr-xr-x  4 smochida  staff    128  3 27 14:30 src

$ cat hello.classlist | grep maven
org/apache/maven/wrapper/MavenWrapperMain
org/apache/maven/wrapper/Downloader
org/apache/maven/wrapper/cli/SystemPropertiesCommandLineConverter
org/apache/maven/wrapper/cli/AbstractPropertiesCommandLineConverter
org/apache/maven/wrapper/cli/AbstractCommandLineConverter
org/apache/maven/wrapper/cli/CommandLineConverter
org/apache/maven/wrapper/cli/CommandLineParser
org/apache/maven/wrapper/cli/CommandLineParser$ParserState
org/apache/maven/wrapper/cli/CommandLineParser$BeforeFirstSubCommand
org/apache/maven/wrapper/cli/CommandLineParser$OptionAwareParserState
org/apache/maven/wrapper/cli/CommandLineParser$AfterOptions
org/apache/maven/wrapper/cli/CommandLineOption
org/apache/maven/wrapper/cli/ParsedCommandLine
org/apache/maven/wrapper/cli/ParsedCommandLineOption
org/apache/maven/wrapper/cli/CommandLineParser$AfterFirstSubCommand
org/apache/maven/wrapper/cli/CommandLineParser$OptionParserState
org/apache/maven/wrapper/cli/CommandLineParser$UnknownOptionParserState
org/apache/maven/wrapper/cli/CommandLineArgumentException
org/apache/maven/wrapper/cli/CommandLineParser$KnownOptionParserState
org/apache/maven/wrapper/SystemPropertiesHandler
org/apache/maven/wrapper/WrapperExecutor
org/apache/maven/wrapper/WrapperConfiguration
org/apache/maven/wrapper/Installer
org/apache/maven/wrapper/DefaultDownloader
org/apache/maven/wrapper/DefaultDownloader$SystemPropertiesProxyAuthenticator
org/apache/maven/wrapper/PathAssembler
org/apache/maven/wrapper/BootstrapMainStarter
org/apache/maven/wrapper/PathAssembler$LocalDistribution

(2) JVM オプションを変更して mvn コマンドを実行して、ダンプファイルを取得する

$ export MAVEN_OPTS="-XX:+UnlockCommercialFeatures -Xshare:dump -XX:+UseAppCDS -XX:SharedArchiveFile=hello.jsa -XX:SharedClassListFile=hello.classlist"

$ ./mvnw validate
/Users/smochida/tmp/app-cds-sample/j10
narrow_klass_base = 0x0000000800000000, narrow_klass_shift = 3
Allocated temporary class space: 1073741824 bytes at 0x00000008c0000000
Allocated shared space: 3221225472 bytes at 0x0000000800000000
Loading classes to share ...
Loading classes to share: done.
Rewriting and linking classes ...
Rewriting and linking classes: done
Number of classes 1478
    instance classes   =  1400
    obj array classes  =    70
    type array classes =     8
Updating ConstMethods ... done. 
Removing unshareable information ... done. 
Scanning all metaspace objects ... 
Allocating RW objects ... 
Allocating RO objects ... 
Relocating embedded pointers ... 
Relocating external roots ... 
Dumping symbol table ...
Dumping String objects to closed archive heap region ...
Dumping objects to open archive heap region ...
Relocating SystemDictionary::_well_known_klasses[] ... 
Removing java_mirror ... done. 
mc  space:      7456 [  0.0% of total] out of      8192 bytes [ 91.0% used] at 0x0000000800000000
rw  space:   4217752 [ 22.2% of total] out of   4218880 bytes [100.0% used] at 0x0000000800002000
ro  space:   7545072 [ 39.8% of total] out of   7548928 bytes [ 99.9% used] at 0x0000000800408000
md  space:      6160 [  0.0% of total] out of      8192 bytes [ 75.2% used] at 0x0000000800b3b000
od  space:   6649456 [ 35.1% of total] out of   6651904 bytes [100.0% used] at 0x0000000800b3d000
st0 space:    462848 [  2.4% of total] out of    462848 bytes [100.0% used] at 0x00000007bff00000
oa0 space:     61440 [  0.3% of total] out of     61440 bytes [100.0% used] at 0x00000007bfe00000
total    :  18950184 [100.0% of total] out of  18960384 bytes [ 99.9% used]

$ ll
total 37184
drwxr-xr-x  10 smochida  staff       320  3 27 14:37 .
drwxr-xr-x   4 smochida  staff       128  3 27 14:13 ..
-rw-r--r--   1 smochida  staff       261  3 27 14:30 .gitignore
drwxr-xr-x   3 smochida  staff        96  3 27 14:30 .mvn
-rw-r--r--   1 smochida  staff     49005  3 27 14:36 hello.classlist
-r--r--r--   1 smochida  staff  18964480  3 27 14:37 hello.jsa
-rwxr-xr-x   1 smochida  staff      6468  3 27 14:30 mvnw
-rw-r--r--   1 smochida  staff      4994  3 27 14:30 mvnw.cmd
-rw-r--r--   1 smochida  staff      2744  3 27 14:30 pom.xml
drwxr-xr-x   4 smochida  staff       128  3 27 14:30 src

(3) JVM オプションを変更して、 Class Data Sharing をロードさせて mvn コマンドを実行し、時間を計測する

$ export MAVEN_OPTS="-XX:+UnlockCommercialFeatures -Xshare:on -XX:+UseAppCDS -XX:SharedArchiveFile=hello.jsa"

$ time ./mvnw validate
/Users/smochida/tmp/app-cds-sample/j10
[INFO] Scanning for projects...
[INFO] 
[INFO] ---------------------< com.example:app-cds-sample >---------------------
[INFO] Building demo 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.149 s
[INFO] Finished at: 2018-03-27T14:38:28+09:00
[INFO] ------------------------------------------------------------------------

real	0m3.639s
user	0m6.669s
sys	0m0.565s

比較

Java8 で mvn コマンドを実行する

$ time ./mvnw validate
/Users/smochida/tmp/app-cds-sample/j08
[INFO] Scanning for projects...
[INFO] 
[INFO] ---------------------< com.example:app-cds-sample >---------------------
[INFO] Building demo 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.774 s
[INFO] Finished at: 2018-03-27T14:28:53+09:00
[INFO] ------------------------------------------------------------------------

real	0m2.745s
user	0m5.133s
sys	0m0.387s

結果・簡単な考察

  • mvn はプラグインをJVM起動後にロードする仕組みを持っているようで、プラグインの有無にかかわらずロードされるクラスが少なくて、無駄に時間がかかる結果になってしまった…
  • 遅延ロードする仕組みのないようなアプリケーションでないとあまり効果が出ない模様
  • 後で Spring Batch または Guice でつくったバッチアプリケーションなどを試してみたい
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