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Thu Oct 08 08:22:27 HKT 2020
From /weblog/java/features
Invoking Assembly Language Programs using java native interface - http://today.java.net/lpt/a/330 Best practices for using the Java Native Interface - http://www.ibm.com/developerworks/java/library/j-jni/index.html Other library try to simple using native library - https://inside.java/2020/10/06/jextract/
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Tue Jun 02 10:14:05 HKT 2020
From /weblog/java/libraries
Efficient Java Matrix Library (EJML) is a linear algebra library for manipulating real/complex/dense/sparse matrices. Its design goals are; 1) to be as computationally and memory efficient as possible for both small and large matrices, and 2) to be accessible to both novices and experts. These goals are accomplished by dynamically selecting the best algorithms to use at runtime, clean API, and multiple interfaces. EJML is free, written in 100% Java and has been released under an Apache v2.0 license. - http://ejml.org/wiki/index.php?title=Main_Page https://mkyong.com/java/java-mod-examples
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Tue Jun 02 08:28:50 HKT 2020
From /weblog/java/features
Watch service, watch if directory changed - http://www.javacodegeeks.com/2012/02/java-7-watchservice.html Tips of using bytebuffer - http://worldmodscode.wordpress.com[..]2/14/the-java-bytebuffer-a-crash-course/ path : ..\.\Java.txt absolute path : C:\Users\WINDOWS 8\workspace\Demo\..\.\Java.txt canonical path : C:\Users\WINDOWS 8\workspace\Java.txt Read more: http://javarevisited.blogspot.com[..]getcanonicalpath-java.html#ixzz3A8Zya6YG Jump to a position of a file, inputstream.skip() is faster than reader.skip(), and reader.skip() is faster than randomAccessFile. Java & Files: An Introduction - https://www.marcobehler.com/guides/java-files
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Sun Mar 29 18:15:44 HKT 2020
From /weblog/java/concurrency
Even though
private List synchList = Collections.synchronizedList(new LinkedList());
is thread safe, serialize sync List is NOT thread safe for sure. The story is, if you only synchronized the collection, and if we try to get the iterator in concurrent access environment, it will throws currencymodificationexception . For collection is small, may be making defensive copy http://www.javapractices.com/Topic15.cjp is good. Otherwise, in java5, there is concurrency collection. reference: http://jroller.com[..]ntry=collections_synchronizedlist_broken http://jroller.com/page/ctarrington?entry=java_collections_trivia Map operation, include use of FutureTask and putIfAbsent() method from ConcurrentMap. - http://www.javaspecialists.co.za/archive/newsletter.do?issue=125 Other then lterate through the elements, adding and removing elements can also be problem, this article document a few good cases about that - http://rayfd.wordpress.com[..]en-a-synchronized-class-isnt-threadsafe/ Samples of using Queue.drainTo() - http://binkley.blogspot.com[..]rforming-fixed-amounts-of-work-with.html http://tech.puredanger.com/2009/02/28/java-7-transferqueue/ Overview of blockingqueue - http://tutorials.jenkov.com[..]/java-util-concurrent/blockingqueue.html Simple benchmark - http://java-persistence-performance.blogspot.com[..]jvm-performance-part-iii-concurrent.html Multi-thread behaviour - http://vanillajava.blogspot.com[..]hread-safety-issues-with-vector-and.html java.util.concurrent.ConcurrentHashMap VS openhft.collections.SharedHashMap - http://openhft.blogspot.co.uk[..]autilconcurrentconcurrenthashmap-vs.html Why are there so many concurrent queues implementations in Java? - https://vmlens.com/articles/cp/why_so_many_queues/ Why hashmap is not thread safe - https://www.pixelstech.net[..]a-HashMap-is-considered-as-thread-unsafe
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Sun Feb 16 21:39:18 HKT 2020
From /weblog/java/performance
-XX:+PerfDisableSharedMem , prevent locking by sharedmem in linux - http://www.evanjones.ca/jvm-mmap-pause.html How linkedin turn the GC - http://engineering.linkedin.com[..]ughput-and-low-latency-java-applications Using generational & concurrent GC collector - http://www.javacodegeeks.com[..]/04/ibm-jvm-tuning-gencon-gc-policy.html Full VM option list : http://blogs.sun.com/roller/resources/watt/jvm-options-list.html, update for Java7 - http://nerds-central.blogspot.com[..]ot.com/2011/07/all-jvm-7-xx-options.html http://stas-blogspot.blogspot.com[..]ost-complete-list-of-xx-options-for.html A simplified list for some frequency use options - http://rdafbn.blogspot.com.au[..]rbage-collector-guidelines-and-tips.html HotSpot JVM garbage collection options cheat sheet - http://aragozin.blogspot.com[..]spot-jvm-garbage-collection-options.html http://www.oracle.com[..]va/javase/tech/vmoptions-jsp-140102.html An example and story about effect of difference VM parameter affecting the performance - http://www.javaspecialists.eu/archive/Issue191.html Clear the code cache automatically with -XX:+UseCodeCacheFlushing - http://blogs.amd.com[..]time-for-long-running-java-applications/ Discussion about -XX:MinHeapFreeRatio parameter - http://www.gossamer-threads.com[..]s.com/lists/lucene/java-user/44286#44286 The other detailed guide for VM parameters tuning - http://java.sun.com/j2se/1.5/pdf/jdk50_ts_guide.pdf Here is a more simple cookbook - http://java.sun.com/performance/reference/whitepapers/tuning.html A outdated (1.4) , compehensive but still not really too detailed, overview of various GC tuning - http://www.petefreitag.com/articles/gctuning/ Some say following VM parameter is good enough -server -Xmx -XX:+UseParallelGC http://blogs.sun.com[..]/page/binublog?entry=java_tuning_for_xml Some say is useful if you have huge memory -XX:+UseLargePages http://blogs.sun.com[..]dagastine?entry=java_se_tuning_tip_large Some say below parameter keep GC in low pause -XX:MaxGCPauseMillis=5000 Some say below parameter are very optimal -XX:+DisableExplicitGC -XX:+UseConcMarkSweepGC -XX:NewSize=1200m -XX:SurvivorRatio=16 http://www.theserverside.com[..]d.tss?thread_id=41258&ASRC=EM_NNL_347804 Some say those parameter is good -XX:+UseConcMarkSweepGC -XX:ParallelCMSThreads=1 -XX:+CMSIncrementalMode -XX:+CMSIncrementalPacing -XX:CMSIncrementalDutyCycleMin=0 -XX:CMSIncrementalDutyCycle=10 http://blog.mikiobraun.de/2010/08/cassandra-gc-tuning.html Just in case anyone is curious, the flags enabled by -XX:+AggressiveOpts in JDK 1.6.0_25 are: -XX:+EliminateAutoBox -XX:AutoBoxCacheMax=20000 -XX:BiasedLockingStartupDelay=500 -XX:+DoEscapeAnalysis -XX:+OptimizeStringConcat -XX:+OptimizeFill Generate dump with OOME - -XX:+HeapDumpOnOutOfMemoryError GC log sample of -XX:+UseConcMarkSweepGC -XX:PrintFLSStatistics=1 -XX:+PrintGCDetails - https://gist.github.com/1329783 A case study of tuning VM GC parameters - http://plumbr.eu[..]ld-you-trust-the-default-settings-in-jvm Explanation for few performance related VM parameters - http://www.techpaste.com[..]ine-options-jvm-performance-improvement/ Show the exact vm flag that java using - http://matthewkwilliams.com[..]/looking-inside-a-jvm-xxprintflagsfinal/ For G1GC - https://dzone.com[..]e-first-garbage-collector-tuning-flags-1 https://ionutbalosin.com[..]otspot-jvm-performance-tuning-guidelines
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