JVM入門 -メモリ管理編-

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JVMೖ໳  -ϝϞϦ؅ཧฤ- Abe Asami

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ࣗݾ঺հ "CF"TBNJl͖ͷࢠz  େࡕͷϑϦʔϥϯεϓϩάϥϚ IUUQOPDPOPOFU !BBUI +BWB,PUMJO4DBMBͳͲͳͲ

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࠷ۙ΍͍ͬͯΔ͜ͱ https://www.geekhub.jp/  ΤϯδχΞಛԽ߹ಉઆ໌ձΠϕϯτɻ࣍ճ 9/14(౔) ։࠵༧ఆ ʮJava11ʹΑΔ  WebΞϓϦέʔγϣϯ։ൃͰֶͿ  Javaϓϩάϥϛϯάೖ໳ʯൢചத https://www.udemy.com/java11-springbootweb-java/

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͜ͷςʔϚΛબΜͩཧ༝ • ਖ਼௚JVMͷ͜ͱ͸งғؾͰ͔͠ཧղ͍ͯ͠ͳ ͍ͨΊɺษڧ͔͔ͨͬͨ͠Β • ӡ༻ϑΣʔζʹܞΘΔػձ͕গͳ͘ɺύ ϑΥʔϚϯε΍ϝϞϦपΓͷτϥϒϧૺ۰ ܦݧ͕͋·Γͳ͍ɾɾɾ • ࠓ೔͸ϝϞϦ؅ཧͷ࿩͚ͩͰ͢

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ͦ΋ͦ΋JVMͱ͸

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Java VM (JavaԾ૝Ϛγϯ) • JavaόΠτίʔυΛ࣮ߦ͢ΔͨΊͷԾ૝؀ڥ • OSґଘΛٵऩͯ͘͠Ε͍ͯΔ

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JVMʹ͸छྨ͕͋Δ • HotSpot VM, IBM JVM, JRockit, ͳͲͳͲ

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ࠓճ͸HotSpot VMͷ࿩ • Oracle͕ఏڙ͍ͯ͠ΔJVM

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͋ͱࠓճ͸Java8ͷ࿩Ͱ͢ • ͜ͷ͋ͱͷݕূͰ࢖ͬͨͷ͕Java8

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JVMͷ࢓૊Έ (ΊͬͪΌͬ͘͟Γ)

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ϝϞϦߏ଄

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࣮ࡍͷϓϩάϥϜͰ GCͷঢ়گΛղੳͯ͠ΈΔ

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GCϩά • GCͷॲཧ࣌ؒ΍લޙͷϝϞϦ࢖༻ྔͳͲͷϩ ά

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GCViewer • GCϩάͷϏϡʔΞʔ • https://github.com/chewiebug/GCViewer • 2019/07/18 ݱࡏɺJDK11ະରԠ

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ͱΓ͋͑ͣɺ ͳΜ͔͠Βಈ͔ͯ͠ GCϩάΛग़ͯ͠ΈΔ

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ࢀর͕࢒Βͳ͍ΠϯελϯεΛ  ͻͨ͢Βੜ੒

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࣮ߦ java -Xloggc:gc.log -XX:+PrintGCDetails -XX:+PrintGCDateStamps Main GCϩάग़ྗͷͨΊͷΦϓγϣϯ (※ඪ४ग़ྗʹग़͚ͩ͢Ͱ͋Ε͹   -verbose:gc ͚͚ͩͭΕ͹OK)

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ग़ྗ͞Εͨϩά

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GCViewerͰ։͍ͯΈΔ

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ΦϒδΣΫτ͸·ͣYoungྖҬʹ࡞ΒΕɺ  ੜ੒͔Β͕࣌ؒܦͭͱOldྖҬʹҠಈ͢Δ

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ࠓճ͸OldྖҬ΁ͷҠಈ͕ൃੜ͠ͳ͍ͨΊ  ώʔϓશମͷ࢖༻ྔ ≒ YoungྖҬͷώʔϓ࢖༻ྔ

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GC࣌ʹͪΌΜͱϝϞϦ͕ղ์͞Ε͍ͯΔ

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ϚΠφʔGCɾɾɾYoungྖҬͷΈ͕ର৅ YoungྖҬ͕  ͍ͬͺ͍ʹͳͬͨ  λΠϛϯάͰ  ϚΠφʔGC͕  ࣮ߦ͞Ε͍ͯΔ

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΋͏1ύλʔϯ  ࢼͯ͠ΈΔ

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ࢀর͕࢒ΔΠϯελϯεΛ  ͻͨ͢Βੜ੒

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GCϩά

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͜Ε΋GCViewerͰ։͍ͯΈΔ

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Full GC (ϝδϟʔGC)ɾɾɾશώʔϓྖҬ͕ର৅

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Full GC͸͕͔͔࣌ؒΔ 2019-07-18T07:28:35.759-0900: 53.145: [GC (Allocation Failure) [PSYoungGen: 1153507K->190965K(1768960K)] 1400776K->506242K(2118656K), 0.3026525 secs] [Times: user=2.55 sys=0.14, real=0.31 secs] 2019-07-18T07:28:36.064-0900: 53.450: [Full GC (Ergonomics) [PSYoungGen: 190965K->190932K(1768960K)] [ParOldGe 315276K->290297K(610816K)] 506242K->481229K(2379776K), [Metaspace: 2676K->2676K(1056768K)], 4.7517463 secs] [Times: user=29.92 sys=0.06, real=4.75 secs] ্ͷϚΠφʔGC ɾɾɾ 0.31 secs  ԼͷFull GC ɾɾɾ 4.75 secs

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GCத͸ΞϓϦέʔγϣϯ  εϨου͕ࢭ·Δ Stop the World (STW) ͱݺ͹ΕΔ

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OutOfMemoryError(OOME) Λൃੜͤͯ͞ΈΔ

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ώʔϓͷ࠷େαΠζΛมߋ  ͯ͠ΈΔ % java -Xms600m -Xmx800m -Xloggc:gc.log -XX:+PrintGCDetails -XX: +PrintGCDateStamps Main -Xms ɾɾɾώʔϓͷॳظαΠζ  -Xmx ɾɾɾώʔϓͷ࠷େαΠζ

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ແࣄ(?) OOMEൃੜ

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GCϩά

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΋͏ͪΐͬͱৄ͘͠ղੳΛ  ͯ͠ΈΔ

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ώʔϓμϯϓ • ಛఆͷ࣌ࠁʹώʔϓ಺ʹؚ·ΕΔ͢΂ͯͷΦϒ δΣΫτͷεφοϓγϣοτ

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OOMEൃੜ࣌ʹώʔϓμϯϓΛ ग़ྗͤͯ͞ΈΔ java -Xms600m -Xmx800m -Xloggc:gc.log -XX:+PrintGCDetails -XX: +PrintGCDateStamps -XX:+HeapDumpOnOutOfMemoryError Main -XX:+HeapDumpOnOutOfMemoryError  ɾɾɾ OOMEൃੜ࣌ʹώʔϓμϯϓΛग़ྗ

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The Eclipse Memory Analyzer • Eclipse Memory Analyzer Open Source Project | The Eclipse Foundation  https://www.eclipse.org/mat/ • ώʔϓμϯϓΛ͍͍ײ͡ʹදࣔͯ͘͠ΕΔGUI πʔϧ

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ώʔϓμϯϓΛ։͍ͯΈͨ

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·ͱΊ • ͜͏͍ͬͨJVMͷجຊ΍໰୊ൃੜ࣌ͷղੳํ ๏Λ஌͓ͬͯ͘ͱɺ͍͟ͱ͍͏ͱ͖ʹ߄ͯͳ ͯ͘ศར(ଟ෼)

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ͪͳΈʹJava11ͷσʔλ෼ੳʹ͸  Java Mission ControlΛ࢖͏ͱ͍͍ͦ͏Ͱ͢ • Java Mission Control   https://www.oracle.com/technetwork/jp/ java/javaseproducts/mission-control/ index.html • ༗ঈػೳ͕ͩͬͨɺJava11͔ΒOpenJDKʹ دଃ͞Εͯແঈఏڙͱͳͬͨ

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ࢀߟʹͨ͠ϖʔδ • OutOfMemoryError ͷௐ΂ํ - Qiita https://qiita.com/opengl-8080/items/ 64152ee9965441f7667b • Java͸ͲͷΑ͏ʹಈ͘ͷ͔ʙਤղͰΘ͔ΔJVMͷ࢓૊Έɿ࿈ࡌʛgihyo.jp … ٕज़ධ࿦ࣾ http://gihyo.jp/dev/serial/01/jvm-arc • ʮϝϞϦʔΛҙࣝͯ͠ΈΑ͏ʯୈ2ճɹGCͷ࢓૊ΈΛཧղ͢Δ | ೔ܦ xTECH ʢΫϩεςοΫʣ https://tech.nikkeibp.co.jp/it/article/COLUMN/ 20060612/240657/?rt=nocnt • ·͡ΊʹJVMνϡʔχϯά: ୈ1ճ ·ͣ͸ݱঢ়֬ೝ https://x1.inkenkun.com/ archives/367

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͝ਗ਼ௌ  ͋Γ͕ͱ͏͍͟͝·ͨ͠