Kris Mok rednaxelafx
rednaxelafx
/ test_memset.c
Created
April 21, 2011 12:29
Show x64 calling convention, demo'd with a call to memset(). GCC's memset is a builtin function, to disable it, use -fno-builtin. Refer to http://en.wikipedia.org/wiki/X86_calling_conventions#System_V_AMD64_ABI_convention
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| #include <string.h> | |
| int main() { | |
| memset(0x42, 42, 37); | |
| return 0; | |
| } |
rednaxelafx
/ .hotspotrc
Created
May 2, 2011 16:15
A demo on GC performance impact differences between an int[] and an Integer[] (on 64-bit HotSpot VM, 19.0-b09)
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| # print out GC detail log | |
| +PrintGCDetails | |
| # make the GC logs simpler by disabling a scavenge before the System.gc()s | |
| -ScavengeBeforeFullGC | |
| # set heap size big enough to hold the array in the demo | |
| InitialHeapSize=2g | |
| MaxHeapSize=2g |
rednaxelafx
/ irb session
Created
May 3, 2011 09:57
Ruby system() http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/35218?help-en
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| D:\experiment>ruby -v | |
| ruby 1.8.6 (2008-08-11 patchlevel 287) [i386-mswin32] | |
| D:\experiment>irb | |
| irb(main):001:0> system 'echo 123' | |
| 123 | |
| => true | |
| irb(main):002:0> system '@echo 123' | |
| => false | |
| irb(main):003:0> quit |
rednaxelafx
/ CLHSDB session
Created
May 5, 2011 07:52
Another demo on primitive type arrays and wrapper type arrays in a Java program running on HotSpot, using SA on a core dump. Env: JDK6u25, x64, -Xmx10m (-server and -XX:+UseCompressedOops are on by default)
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| $ java -version | |
| java version "1.6.0_25" | |
| Java(TM) SE Runtime Environment (build 1.6.0_25-b06) | |
| Java HotSpot(TM) 64-Bit Server VM (build 20.0-b11, mixed mode) | |
| $ alias -p | grep clhsdb | |
| alias clhsdb='java -classpath .:$JAVA_HOME/lib/sa-jdi.jar sun.jvm.hotspot.CLHSDB' | |
| $ clhsdb | |
| hsdb> help | |
| Available commands: | |
| assert true | false |
rednaxelafx
/ gist:971134
Created
May 13, 2011 19:20
A compilation log showing the effects of tiered system of HotSpot 20 build 11 (JDK6u25) on x64. The command used was: jconsole -J-XX:+TieredCompilation -J-XX:+PrintCompilation
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| 56 1 3 java.lang.String::hashCode (64 bytes) | |
| 57 2 3 java.lang.String::equals (88 bytes) | |
| --- n java.lang.System::arraycopy (static) | |
| 58 3 3 java.lang.String::charAt (33 bytes) | |
| 58 5 3 java.lang.Object::<init> (1 bytes) | |
| 58 4 3 java.lang.Math::min (11 bytes) | |
| 62 6 3 java.nio.Buffer::position (43 bytes) | |
| 62 9 3 java.nio.charset.CoderResult::isUnderflow (13 bytes) | |
| 63 7 3 java.util.jar.Attributes$Name::isValid (32 bytes) | |
| 63 8 3 java.util.jar.Attributes$Name::isAlpha (30 bytes) |
rednaxelafx
/ .hotspot_compiler
Created
May 15, 2011 06:49
Example of code reordering from with HotSpot 20. Run on JDK6u25.
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| dontinline TestC2BranchPrediction conditionalBranch | |
| dontinline TestC2BranchPrediction marker |
rednaxelafx
/ Make udis86
Created
May 16, 2011 04:06
Use udis86 to disassemble instructions in a JVM crash log
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| $ wget http://prdownloads.sourceforge.net/udis86/udis86-1.7.tar.gz?download | |
| $ tar zxvf udis86-1.7.tar.gz | |
| $ cd udis86-1.7 | |
| $ ./configure | |
| $ make | |
| $ cd udcli |
rednaxelafx
/ .hotspotrc
Created
May 18, 2011 10:35
Use JMX to make HPROF heap dumps right before and after a full GC
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| +PrintGCDetails |
rednaxelafx
/ gist:997679
Created
May 29, 2011 11:45
prtstat example: using prtstat on a groovysh process on Ubuntu 10.10 x64
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| $ prtstat 4394 | |
| Process: java State: S (sleeping) | |
| CPU#: 2 TTY: 136:39 Threads: 16 | |
| Process, Group and Session IDs | |
| Process ID: 4394 Parent ID: 4341 | |
| Group ID: 4394 Session ID: 4341 | |
| T Group ID: 4394 | |
| Page Faults | |
| This Process (minor major): 64582 18 |
rednaxelafx
/ gist:998011
Created
May 29, 2011 18:23
See the default values of various sizes set by a J9 VM, with -verbose:sizes
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| $ java -version | |
| java version "1.6.0" | |
| Java(TM) SE Runtime Environment (build pxa6460sr8fp1-20100624_01(SR8 FP1)) | |
| IBM J9 VM (build 2.4, JRE 1.6.0 IBM J9 2.4 Linux amd64-64 jvmxa6460sr8ifx-20100609_59383 (JIT enabled, AOT enabled) | |
| J9VM - 20100609_059383 | |
| JIT - r9_20100401_15339ifx2 | |
| GC - 20100308_AA) | |
| JCL - 20100624_01 | |
| $ java -verbose:sizes | |
| -Xmca32K RAM class segment increment |