- The document discusses optimizing Java performance on hardware by leveraging features like AES-NI, transparent huge pages, and compiler intrinsics. - It provides examples showing performance improvements from using these features, such as faster encryption times when enabling AES-NI and fewer TLB misses with transparent huge pages. - It also discusses Java VM options, garbage collection, and the HotSpot compiler related to hardware optimization.

1. 末永 恭正 @YaSuenag

2. 今日はGCの話をあまりしません！
他の方の資料等をご覧ください…
OracleとJavaは、Oracle Corporation及びその子会社、関連会社の米国及びその他の国における登録商標です。
文中の社名、商品名等は各社の商標または登録商標である場合があります。
本資料の実装確認はOpenJDK8 8u-dev（HotSpot rev. 7164:bf68e15dc8fe）で行っています。

3. ハードウェアをちょっと気にして
HotSpotを気持ちよく動かしてあげよう！
※AMD64 Linuxを中心にお話しします

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http://icedtea.classpath.org/wiki/HeapStats/jp

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8. $ java -version
openjdk version "1.8.0_31"
OpenJDK Runtime Environment (build 1.8.0_31-b13)
OpenJDK 64-Bit Server VM (build 25.31-b07, mixed mode)
$ java -version
java version "1.8.0"
Java(TM) SE Runtime Environment (build 1.8.0-b132)
Java HotSpot(TM) Client VM (build 25.0-b70, mixed mode)

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• http://docs.oracle.com/javase/jp/8/technotes/guides/vm/index.html

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• http://otndnld.oracle.co.jp/ondemand/javaday2014/pdf/C
2-JavaDay-304328.pdf

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• http://docs.oracle.com/javase/jp/8/technotes/guides/vm/s
erver-class.html
注: Java SE 6の場合、server-classマシンとは、少なくとも2つのCPU
と、最少でも2Gバイトの物理メモリーを備えているマシンを指し
ます。

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15. •
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• MetaspaceはGC対象ではありません！
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ちょっと
だけ

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• http://www.slideshare.net/YujiKubota/concurrent-
marksweep-garbage-collection

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• http://www.slideshare.net/YaSuenag/metaspace

18. • CodeCacheはGCでクリアされません！
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ちょっと
だけ
Java HotSpot(TM) 64-Bit Server VM warning: CodeCache is full. Compiler has been disabled.
Java HotSpot(TM) 64-Bit Server VM warning: Try increasing the code cache size using -XX:ReservedCodeCacheSize=
CodeCache: size=2496Kb used=1955Kb max_used=1969Kb free=540Kb
bounds [0x00007f50c844b000, 0x00007f50c86bb000, 0x00007f50c86bb000]
total_blobs=578 nmethods=353 adapters=139
compilation: disabled (not enough contiguous free space left)

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• http://www.oracle.com/webfolder/technetwork/jp/javama
gazine/Java-JA13-Architect-evans.pdf

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$ ulimit -v 102400
$ /usr/local/jdk1.8.0/bin/java -version
#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (malloc) failed to allocate 80 bytes for AllocateHeap
# An error report file with more information is saved as:
# /home/xxx/hs_err_pid8664.log

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• http://www.oracle.com/technetwork/jp/articles/java/compressedoops-
427542-ja.html
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# cat /sys/kernel/mm/transparent_hugepage/enabled
always [madvise] never

27. import java.nio.*;
import java.nio.file.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.security.*;
public class AESTest{
public static void main(String[] args) throws Exception{
Key key = new SecretKeySpec("passwordpassword".getBytes(), "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE, key);
byte[] plain = Files.readAllBytes(Paths.get(args[0]));
long start = System.currentTimeMillis();
cipher.doFinal(plain);
long end = System.currentTimeMillis();
long elapsedTime = end - start;
System.out.println("Elapsed time: " + elapsedTime + " ms");
}
}

28. $ java -Xms2g -Xmx2g AESTest /tmp/test.dat
Elapsed time: 1654 ms
$ java -Xms2g -Xmx2g -XX:+UseTransparentHugePages AESTest /tmp/test.dat
Elapsed time: 1613 ms
約40msの差！
ソフトウェア環境：
• Fedora21 x86_64
• kernel-3.18.7-200.fc21.x86_64
• glibc-2.20-8.fc21.x86_64
• java-1.8.0-openjdk-1.8.0.31-5.b13.fc21.x86_64
ハードウェア環境：
• CPU：Intel Core i5 2500T
• MB：GIGABYTE GA-H67A-UD3H-B3
• メモリ：DDR3 1333MHz 2GB×2
テストデータ：
• /tmp/test.dat
• /dev/urandomから500MBを/tmp配下にコピー
• /tmpはtmpfs

29. $ perf stat -e dTLB-load-misses,dTLB-store-misses java -Xms2g -Xmx2g AESTest /tmp/test.dat
Elapsed time: 1654 ms
Performance counter stats for 'java -Xms2g -Xmx2g AESTest /tmp/test.dat':
826,055 dTLB-load-misses
1,648,456 dTLB-store-misses
2.300445236 seconds time elapsed
$ perf stat -e dTLB-load-misses,dTLB-store-misses java -Xms2g -Xmx2g -XX:+UseTransparentHugePages AESTest /tmp/test.dat
Elapsed time: 1613 ms
Performance counter stats for 'java -Xms2g -Xmx2g -XX:+UseTransparentHugePages AESTest /tmp/test.dat':
623,795 dTLB-load-misses
576,097 dTLB-store-misses
2.165985041 seconds time elapsed
TLBミスヒットが激減！

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33. 論理プロセッサ数が8以下のとき
論理プロセッサ数が9以上のとき
論理プロセッサ数と同数
8 +
5 < 論理プロセッサ数 > −8
8

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• http://openjdk.java.net/jeps/157

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• http://openjdk.java.net/projects/code-tools/jol/

37. import sun.misc.Contended;
@Contended
public class Test{
public int val1;
public int val2;
public int val3;
public int val4;
public int val5;
}

38. $ java -cp jol-cli-0.3.1-full.jar:.
org.openjdk.jol.Main internals Test
：
Test object internals:
OFFSET SIZE TYPE DESCRIPTION VALUE
：
12 4 int Test.val1 0
16 4 int Test.val2 0
20 4 int Test.val3 0
24 4 int Test.val4 0
28 4 int Test.val5 0
Instance size: 32 bytes (reported by Instrumentation API)
Space losses: 0 bytes internal + 0 bytes external = 0 bytes total
$ java -XX:-RestrictContended -cp jol-cli-0.3.1-full.jar:.
org.openjdk.jol.Main internals Test
：
Test object internals:
OFFSET SIZE TYPE DESCRIPTION VALUE
：
12 128 (alignment/padding gap) N/A
140 4 int Test.val1 0
144 4 int Test.val2 0
148 4 int Test.val3 0
152 4 int Test.val4 0
156 4 int Test.val5 0
160 128 (loss due to the next object alignment)
Instance size: 288 bytes (reported by Instrumentation API)
Space losses: 128 bytes internal + 128 bytes external = 256 bytes total
@Contended無効 @Contended有効
ソフトウェア環境：
• Fedora21 x86_64
• kernel-3.18.7-200.fc21.x86_64
• glibc-2.20-8.fc21.x86_64
• java-1.8.0-openjdk-1.8.0.31-5.b13.fc21.x86_64

39. import sun.misc.Contended;
public class Test2{
@Contended("group")
public int val1;
@Contended("group")
public int val2;
public int val3;
public int val4;
@Contended
public int val5;
}

40. $ java -cp jol-cli-0.3.1-full.jar:.
org.openjdk.jol.Main internals Test2
：
Test2 object internals:
OFFSET SIZE TYPE DESCRIPTION VALUE
：
12 4 int Test2.val1 0
16 4 int Test2.val2 0
20 4 int Test2.val3 0
24 4 int Test2.val4 0
28 4 int Test2.val5 0
Instance size: 32 bytes (reported by Instrumentation API)
Space losses: 0 bytes internal + 0 bytes external = 0 bytes total
$ java -XX:-RestrictContended -cp jol-cli-0.3.1-full.jar:.
org.openjdk.jol.Main internals Test2
：
Test2 object internals:
OFFSET SIZE TYPE DESCRIPTION VALUE
：
12 4 int Test2.val3 0
16 4 int Test2.val4 0
20 128 (alignment/padding gap) N/A
148 4 int Test2.val5 0
152 128 (alignment/padding gap) N/A
280 4 int Test2.val1 0
284 4 int Test2.val2 0
288 128 (loss due to the next object alignment)
Instance size: 416 bytes (reported by Instrumentation API)
Space losses: 256 bytes internal + 128 bytes external = 384 bytes total
@Contended無効 @Contended有効
ソフトウェア環境：
• Fedora21 x86_64
• kernel-3.18.7-200.fc21.x86_64
• glibc-2.20-8.fc21.x86_64
• java-1.8.0-openjdk-1.8.0.31-5.b13.fc21.x86_64

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• http://www.oracle.com/technetwork/java/faq-sun-packages-
142232.html
sun.miscパッケージです！

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44. UseSSE
UseAVX
UseAES
UseCLMUL
UseXmmLoadAndClearUpper UseXmmRegToRegMoveAll
UseXMMForArrayCopy
UseUnalignedLoadStores
UseCountLeadingZerosInstruction
UseCountTrailingZerosInstruction
UseBMI1Instructions
UseBMI2Instructions
UsePopCountInstruction
UseFastStosb
AllocatePrefetchInstr
UseRTMLocking
UseRTMForStackLocks
UseSSE42Intrinsics
UseRTMXendForLockBusy

45. import java.nio.*;
import java.nio.file.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.security.*;
public class AESTest{
public static void main(String[] args) throws Exception{
Key key = new SecretKeySpec("passwordpassword".getBytes(), "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE, key);
byte[] plain = Files.readAllBytes(Paths.get(args[0]));
long start = System.currentTimeMillis();
cipher.doFinal(plain);
long end = System.currentTimeMillis();
long elapsedTime = end - start;
System.out.println("Elapsed time: " + elapsedTime + " ms");
}
}

46. $ java -Xms2g -Xmx2g AESTest /tmp/test.dat
Elapsed time: 1669 ms
$ java -Xms2g -Xmx2g -XX:-UseAES AESTest /tmp/test.dat
Elapsed time: 4651 ms
ソフトウェア環境：
• Fedora21 x86_64
• kernel-3.18.7-200.fc21.x86_64
• glibc-2.20-8.fc21.x86_64
• java-1.8.0-openjdk-1.8.0.31-5.b13.fc21.x86_64
約3秒差！
テストデータ：
• /tmp/test.dat
• /dev/urandomから500MBを/tmp配下にコピー
• /tmpはtmpfs
ハードウェア環境：
• CPU：Intel Core i5 2500T
• MB：GIGABYTE GA-H67A-UD3H-B3
• メモリ：DDR3 1333MHz 2GB×2

47. $ java -XX:+UnlockDiagnosticVMOptions -XX:+PrintIntrinsics AESTest /tmp/test.dat
@ 64 com.sun.crypto.provider.AESCrypt::encryptBlock (953 bytes) (intrinsic)
@ 80 java.lang.System::arraycopy (0 bytes) (intrinsic)
Elapsed time: 1669 ms
$ java -XX:+UnlockDiagnosticVMOptions -XX:+PrintIntrinsics -XX:-UseAES AESTest /tmp/test.dat
@ 80 java.lang.System::arraycopy (0 bytes) (intrinsic)
Elapsed time: 4651 ms

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• http://www.intel.co.jp/content/www/jp/ja/architecture-and-
technology/advanced-encryption-standard--aes-/data-protection-aes-
general-technology.html
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→AES-NI命令セットを活用した機械語がJITで適用された！

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• http://openjdk.java.net/projects/sumatra/
• https://wiki.openjdk.java.net/display/Sumatra/Main
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53. https://wiki.openjdk.java.net/display/Sumatra/Standalone+Sumatra+Stream+API+Offload+Demo
final int length = 8;
int[] ina = new int[length];
int[] inb = new int[length];
int[] out = new int[length];
// Initialize the input arrays - this is offloadable
IntStream.range(0, length).parallel().forEach(p -> {
ina[p] = 1;
inb[p] = 2;
});
// Sum each pair of elements into out[] - this is offloadable
IntStream.range(0, length).parallel().forEach(p -> {
out[p] = ina[p] + inb[p];
});

54. We cannot speak for Project Sumatra or AMD. Project Graal decided to temporarily
remove the compiler's GPU support, because the original contributors
indicated to no longer maintain the code. We are still investigating outside
the main branch a new version of compilation support for heterogenous
architectures for Graal. If you want to compile and run a Graal version with GPU support in
the meantime, use this revision: http://hg.openjdk.java.net/graal/graal/rev/91fee1fab96d
<http://hg.openjdk.java.net/graal/graal/rev/91fee1fab96d>.
http://mail.openjdk.java.net/pipermail/sumatra-dev/2015-February/000308.html

55. HSA/PTXサポート削除
GPUを使いたければこのタグを使用→

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• ツールの動作を知ることがHotSpotを知る一番の近道！

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• http://www.slideshare.net/YaSuenag/serviceability-tools

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• http://www.oracle.com/webfolder/technetwork/jp/javama
gazine/Java-JA12-architect-bajaj.pdf

60. HotSpotがご機嫌ナナメになったら
取るべき情報は取っておこう！

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• http://www.slideshare.net/agetsuma/java-34815905

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64. • だいたい
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• クラッシュ解析の最初の取っ掛かり！

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Current thread (0x00007fb944008800): JavaThread "main" [_thread_in_native, id=10054, stack(0x00007fb9486b0000,0x00007fb9487b1000)]
siginfo: si_signo: 11 (SIGSEGV), si_code: 1 (SEGV_MAPERR), si_addr: 0x0000000000000000

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Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
C [libsegv.so+0x6a0] Java_NativeSEGV_doSEGV+0x18
j NativeSEGV.doSEGV()V+0
j NativeSEGV.main([Ljava/lang/String;)V+0
v ~StubRoutines::call_stub
V [libjvm.so+0x681a56] JavaCalls::call_helper(JavaValue*, methodHandle*, JavaCallArguments*, Thread*)+0x1056
V [libjvm.so+0x6c36c2] jni_invoke_static(JNIEnv_*, JavaValue*, _jobject*, JNICallType, _jmethodID*, JNI_ArgumentPusher*, Thread*)+0x362
V [libjvm.so+0x6e00ca] jni_CallStaticVoidMethod+0x17a
C [libjli.so+0x7bcc] JavaMain+0x80c
C [libpthread.so.0+0x752a]

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• https://bugs.openjdk.java.net/
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：
compile java/lang/invoke/MethodHandle <clinit> ()V -1 4 inline 1 0 -1 java/lang/invoke/MethodHandle <clinit> ()V

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Current CompileTask:
C2: 13427 2 !b 4 java.lang.invoke.MethodHandle::<clinit> (75 bytes)

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• https://github.com/YaSuenag/JVMLive
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