Blog: JVM agents and JIT

fast jvm

$ javac test.java
$ time java  -cp . test -runPremain
exitting

real    0m0.629s
user    0m1.282s
sys     0m0.083s

fast jvm profiling

$ java -cp . -agentpath:/root/perf/async-profiler-master/build/libasyncProfiler.so=start,file=foo test -runPremain
$ cat perf
....
          ns  percent  samples  top
  ----------  -------  -------  ---
   140071867   23.33%       14  sun.security.provider.SHA2.implCompress
   110105345   18.34%       11  Method::make_jmethod_id(ClassLoaderData*, Method*)
    20016638    3.33%        2  Rewriter::scan_method(Method*, bool, bool*)
    20009898    3.33%        2  __malloc
    19997059    3.33%        2  sun.security.provider.SHA.implCompress
    10022555    1.67%        1  _raw_spin_unlock_irqrestore_[k]
    10016146    1.67%        1  __do_page_fault_[k]
    10011639    1.67%        1  __GI___pthread_mutex_lock
    10011504    1.67%        1  java_lang_String::equals(oopDesc*, unsigned short*, int)
    10011372    1.67%        1  Interpreter
    10009534    1.67%        1  java.io.ByteArrayInputStream.available
    10009404    1.67%        1  __pthread_getspecific
...

fast JVM with PrintCompilation

 $ java -XX:+UnlockDiagnosticVMOptions -XX:+PrintCompilation  -cp . test -runPremain | grep 'sun.security.provider.SHA2.'
    ...
    192  206       3       sun.security.provider.SHA2::lf_S (11 bytes)
    193  207       3       sun.security.provider.SHA2::lf_R (4 bytes)
    193  209       3       sun.security.provider.SHA2::lf_sigma1 (21 bytes)
    193  210       3       sun.security.provider.SHA2::lf_ch (10 bytes)
    193  211       3       sun.security.provider.SHA2::lf_sigma0 (20 bytes)
    ...

jstack

$ jstack 24692
...
"main" #1 prio=5 os_prio=0 tid=0x00007f228000a000 nid=0x6075 runnable [0x00007f2287823000]
   java.lang.Thread.State: RUNNABLE
        at sun.security.provider.SHA2.implCompress(SHA2.java:201)
        at sun.security.provider.DigestBase.implCompressMultiBlock(DigestBase.java:141)
        at sun.security.provider.DigestBase.engineUpdate(DigestBase.java:128)
        at java.security.MessageDigest$Delegate.engineUpdate(MessageDigest.java:584)
        at java.security.MessageDigest.update(MessageDigest.java:335)
        at com.sun.crypto.provider.HmacCore.engineUpdate(HmacCore.java:161)
        at javax.crypto.Mac.update(Mac.java:485)
        at com.sun.crypto.provider.PBKDF2KeyImpl.deriveKey(PBKDF2KeyImpl.java:178)
        at com.sun.crypto.provider.PBKDF2KeyImpl.<init>(PBKDF2KeyImpl.java:113)
        at com.sun.crypto.provider.PBKDF2Core.engineGenerateSecret(PBKDF2Core.java:69)
        at javax.crypto.SecretKeyFactory.generateSecret(SecretKeyFactory.java:336)
        at com.mmp.jvmtiperf.MyAgent.decrypt(MyAgent.java:17)
        at com.mmp.jvmtiperf.MyAgent.premain(MyAgent.java:28)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:386)
        at sun.instrument.InstrumentationImpl.loadClassAndCallPremain(InstrumentationImpl.java:401)

MyAgent.java

package com.mmp.jvmtiperf;

import javax.crypto.spec.*;
import java.lang.instrument.Instrumentation;
import java.security.spec.*;
import java.util.Base64;
import javax.crypto.*;

public class MyAgent {

    public static String decrypt(String strToDecrypt, String secret) {
        try {
            byte[] iv = new byte[16];
            IvParameterSpec ivspec = new IvParameterSpec(iv);
            SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
            KeySpec spec = new PBEKeySpec(secret.toCharArray(), "hello@123".getBytes(), 65536, 256);
            SecretKey tmp = factory.generateSecret(spec);
            SecretKeySpec secretKey = new SecretKeySpec(tmp.getEncoded(), "AES");
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
            cipher.init(2, secretKey, ivspec);
            return new String(cipher.doFinal(Base64.getDecoder().decode(strToDecrypt)));
        } catch (Exception e) {
            return null;
        }
    }

    public static void premain(String agentArgs, Instrumentation inst) {
        System.setProperty("mySecretProp",
           decrypt("89/LaUAGfN8VMrUew8wuylMyzgcCxC6Af4DVLROEouw=", "supersecret"));
    }
}

package.sh

$ javac MyAgent.java
$ mkdir -p com/mmp/jvmtiperf
$ cp MyAgent.class com/mmp/jvmtiperf
$ mkdir META-INF
$ echo "Manifest-Version: 1.0
Implementation-Title:   myagent
Premain-Class: com.mmp.jvmtiperf.MyAgent
Implementation-Version: 1.0.0" > META-INF/MANIFEST.MF
$ jar cvf myagent.jar com/mmp/jvmtiperf
$ zip myagent.jar META-INF/MANIFEST.MF 

profiler output

--- 10001689 ns (0.04%), 1 sample
  [ 0] sun.misc.Unsafe.getInt
  [ 1] sun.security.provider.ByteArrayAccess.b2iBig64
  [ 2] sun.security.provider.SHA2.implCompress
  [ 3] sun.security.provider.SHA2.implDigest
  [ 4] sun.security.provider.DigestBase.engineDigest
  [ 5] sun.security.provider.DigestBase.engineDigest
  [ 6] java.security.MessageDigest$Delegate.engineDigest
  [ 7] java.security.MessageDigest.digest
  [ 8] com.sun.crypto.provider.HmacCore.engineDoFinal
  [ 9] javax.crypto.Mac.doFinal
  [10] javax.crypto.Mac.doFinal
  [11] com.sun.crypto.provider.PBKDF2KeyImpl.deriveKey
  [12] com.sun.crypto.provider.PBKDF2KeyImpl.<init>
  [13] com.sun.crypto.provider.PBKDF2Core.engineGenerateSecret
  [14] javax.crypto.SecretKeyFactory.generateSecret
  [15] com.mmp.jvmtiperf.MyAgent.decrypt
  [16] com.mmp.jvmtiperf.MyAgent.premain
  [17] sun.reflect.NativeMethodAccessorImpl.invoke0
  [18] sun.reflect.NativeMethodAccessorImpl.invoke
  [19] sun.reflect.DelegatingMethodAccessorImpl.invoke
  [20] java.lang.reflect.Method.invoke
  [21] sun.instrument.InstrumentationImpl.loadClassAndStartAgent
  [22] sun.instrument.InstrumentationImpl.loadClassAndCallPremain

          ns  percent  samples  top
  ----------  -------  -------  ---
 13747492952   52.44%     1374  sun.security.provider.SHA2.lf_S
  1920993571    7.33%      192  sun.security.provider.SHA2.implCompress
  1801015904    6.87%      180  sun.security.provider.SHA2.lf_R
  1190642160    4.54%      119  sun.security.provider.SHA2.lf_maj
  1160569433    4.43%      116  sun.security.provider.SHA2.lf_ch
  1040701461    3.97%      104  Interpreter
  1010585056    3.86%      101  sun.security.provider.SHA2.lf_sigma0
   560312244    2.14%       56  sun.security.provider.SHA2.lf_sigma1
   560302440    2.14%       56  sun.security.provider.SHA2.lf_delta1
   560296929    2.14%       56  sun.security.provider.SHA2.lf_delta0
   300184334    1.15%       30  java.lang.Integer.reverseBytes
   170088977    0.65%       17  java.util.Arrays.fill
   160085552    0.61%       16  sun.security.provider.DigestBase.engineUpdate
   150083336    0.57%       15  sun.security.provider.ByteArrayAccess.b2iBig64

slow jvm

$ time java -javaagent:myagent.jar -cp . test
exitting

real    0m32.057s
user    0m32.020s
sys     0m0.054s

slow JVM with PrintCompilation

$ java -XX:+UnlockDiagnosticVMOptions -XX:+PrintCompilation -javaagent:myagent.jar -cp . test   | grep 'sun.security.provider.SHA2::lf_S'
$

test.java

class test {
        public static void main(String a[]) {
                if(a.length > 0 && a[0].equals("-runPremain"))
                        com.mmp.jvmtiperf.MyAgent.premain(a[0], null);
                System.out.println("exitting");
        }
}