Latest news

NEW: AUGUST NEWSLETTER

• We list all the latest Java performance related news and articles
  • "For concurrency, good coding practice competes with good performance - the solution to this dilemma is to factor in the amount of concurrency needed"
• All the latest Java performance tips extracted in concise form
  • "Biased locking is good for un-contended locks, but is worth disabling (-XX:-UseBiasedLocking) if there is contention (monitor with -XX:+PrintSafepointStatistics -XX:+PrintGCApplicationStoppedTime which let's you see safepoint statistics for stopped times)"

JULY NEWSLETTER

• We list all the latest Java performance related news and articles
  • "Seriously horizontally scaled applications monitor the performance of each virtual server and actually shutdown services when they detect sufficient contention for resources from competing virtual containers using the shared hardware"
• All the latest Java performance tips extracted in concise form
  • "Inner classes need to have access to their outer class - if the inner class instance continues to be live when the outer class instance is completed, the outer class instance will be kept alive leading to a possible memory leak. One possible solution is to hold the outer class reference in a weak reference. "

JUNE NEWSLETTER

• We list all the latest Java performance related news and articles
  • "The 'concurrency, data size and responsiveness' 3 axes of performance are particularly useful for characterising the need for performance and memory efficiency during development: they tell you when you need to go beyond good coding practices to achieve performance goals"
• All the latest Java performance tips extracted in concise form
  • "5 ways to do atomic optimistic reads on multiple fields are: StampedLock, AtomicReference, AtomicReferenceFieldUpdater, Unsafe, VarHandle."

MAY NEWSLETTER

• We list all the latest Java performance related news and articles
  • "The slides are available and give you a fairly complete grounding in how to handle all the most common types of performance and memory problems"
• All the latest Java performance tips extracted in concise form
  • "GPUs are suitable where the problem can be massively parallelized, and there is a lot of data that needs processing. Machine learning is an excellent example. GPUs excel at running multiples of the same operation at once."

APRIL NEWSLETTER

• We list all the latest Java performance related news and articles
  • "'ParNew + SerialOld : -XX:+UseParNewGC', was the optimal garbage collector combination if you were targeting footprint size in bi-stable heaps"
• All the latest Java performance tips extracted in concise form
  • "Java 9 recommended GC logging parameters are -Xlog:gc*,gc+ref=debug,gc+age=trace,gc+heap=debug:file=gc%p%t.log:tags,uptime,time:filecount=10,filesize=10m (you may need to delete some options for your use)"

MARCH NEWSLETTER

• We list all the latest Java performance related news and articles
  • "If you really want to have memory-pressure sensitive cache, encapsulate your preferred cache and add separate functionality which detects memory pressure with SoftReference instance just for that"
• All the latest Java performance tips extracted in concise form
  • "Typical tuning options at the CPU level include: reduce the number of instructions needed to execute the algorithm; change the data structure to reduce memory stalls (waiting for memory); change the program logic to reduce branch stalls (eg from mispredicted branches); change the order of operations so that they execute in parallel across the cores more easily (if in a loop each subsequent operation depends on the result of the last one, this is difficult); breakdown long latency operations into multiple simpler ones"

FEBRUARY NEWSLETTER

• We list all the latest Java performance related news and articles
  • "Getting a heap dump is straightforward, you can use any of jmap; the JMX com.sun.management.HotSpotDiagnostic.dumpHeap() method (from any JMX aware tool, such as jconsole); the -XX:+HeapDumpOnOutOfMemoryError flag (which does what it says); and jcmd [PID] GC.heap_dump [PATH_TO_DUMPFILE]"
• All the latest Java performance tips extracted in concise form
  • "jvmstat includes several hundred indicators covering nearly all JVM areas: class loading, garbage collection, multithreading, just-in-time compilation, etc. jvmstat counters are free - Java HotSpot VM exports them anyway, whether you read them or not, in the file system as a memory-mapped file in a temporary directory, by default /tmp/hsperfdata_{user}/{pid}, where {pid} is the JVM process ID"

JANUARY NEWSLETTER

• We list all the latest Java performance related news and articles
  • "I'll be giving a talk at this years Devoxx UK on what I've learned about Java performance tuning over the 15 years of these newsletters"
• All the latest Java performance tips extracted in concise form
  • "If you are considering timescales of 10 microseconds and lower, you need to architect for cores to run independently - so you need to understand the data in the shared CPU cache, and use thread affinity to keep specific operations on specific cores"

DECEMBER NEWSLETTER

• We list all the latest Java performance related news and articles
  • "there's little for diagnosing concurrency issues in production beyond analysing multiple stack traces, data from the ThreadMXBean and jstack -l for java.util.concurrent.locks"
• All the latest Java performance tips extracted in concise form
  • "If you will be sending the same data component repeatedly, you can marshall that once and cache the marshalled form or a reference to it (ideally in a send buffer close to the wire) for improved scalability"

NOVEMBER NEWSLETTER

• We list all the latest Java performance related news and articles
  • "A good performance expert tends to be a good troubleshooter because many of the analysis skills are the same"
• All the latest Java performance tips extracted in concise form
  • "GC pauses with high 'sys' time compared to 'user' can occur from underlying OS IO happening, pausing the JVM. Similarly GC pauses with low 'user' and low 'sys' but high 'real' can be caused from JVM getting stuck waiting for OS IO to complete (including when GC file rotation triggers filesystem flushing). "

OCTOBER NEWSLETTER

• We list all the latest Java performance related news and articles
  • "When 20 nanoseconds per request matter to you, you need to know about Thread.onSpinWait()."
• All the latest Java performance tips extracted in concise form
  • "Accept that the bottlenecks will shape your architecture, and consider them early on."

SEPTEMBER NEWSLETTER

• We list all the latest Java performance related news and articles
  • "jcmd will now be able to alter some fine-grained JIT compiler directives at runtime and you can define them statically at startup; this may be particularly useful for those low latency applications with warmup concerns"
• All the latest Java performance tips extracted in concise form
  • "JEP 269, available in Java 9, adds factory methods for collections which return immutable collections, eg List.of(a, b, c, ...), Map.of(k1, v1, k2, v2, ...). Note that immutable collections are automatically threadsafe. They are also space efficient."

AUGUST NEWSLETTER

• We list all the latest Java performance related news and articles
  • "After that I realised that this is now the most dynamic, interesting, innovative time we've ever seen for Java! More than 20 years of ever improving Java and, instead of maturing and slowing down, we're actually accelerating improvements in Java all the way from the very bottom of the stack on through every stage!"
• All the latest Java performance tips extracted in concise form
  • "In order of increasing complexity for concurrency options: stateless; immutable; synchronized; locks; read-copy-update; java.util.concurrent.atomic; queueing"

JULY NEWSLETTER

• We list all the latest Java performance related news and articles
  • "both 'don't share' and 'don't mutate' techniques tend to increase copies of data, which incurs runtime and garbage collection costs that both impact latency. You gain lower maintenance costs, but it's very hard to maintain high throughput together with low latency with those two techniques. If you need low latency, you need 'coordinate access' and, more specifically, coordinate access using lock-free techniques."
• All the latest Java performance tips extracted in concise form
  • "SSD throughput is typically 2 orders of magnitude higher than HDD, but you can gain up to a further 4x speedup by making the application SSD friendly - eg using multiple concurrrent I/O threads (for small reads; large reads should keep the concurrent I/O thread count low). This differs markedly from HDDs where multiple concurrrent I/O threads tends to actually decrease throughput."

JUNE NEWSLETTER

• We list all the latest Java performance related news and articles
  • "Target having two JVM instances, (three if you need more scale or redundancy), grow those instances up to the NUMA-node size but preferentially try to stay below either 4GB or 32GB max heaps; above NUMA-node RAM you need to test whether a bigger heap single JVM or per-NUMA-node memory restricted JVMs are more efficient"
• All the latest Java performance tips extracted in concise form
  • "The probability that a customer will see a worse than a nth centile request is 1-(n)^requests, eg the average page makes 42 requests to display the page, then 1-(0.95)^24 = 88% of pages see the 95th centile or worse in latency!"

MAY NEWSLETTER

• We list all the latest Java performance related news and articles
  • "An architect's primary approach is to see how the system will scale, handle failure modes staying resilient, and remain secure"
• All the latest Java performance tips extracted in concise form
  • "Why distribute your system? Scale and fault tolerance. But these are in conflict with each other - higher scale means more failure, more failure tolerance means more overhead which reduces scaling. Everything is a tradeoff between these"

Previous newsletters

All our previous newsletters can be viewed from here

How to use this site

This site has four main information resources:

• The uncategorized tips page lists many other web pages with Java performance tuning related information. Each web page has its performance tuning tips extracted and listed immediately after the URL is listed. These tips are being categorized, and the tips page links to those categories currently available. If the performance area you are interested in is not yet categorized, send us an email from this page telling us the categorization you'd like to see. In any of the tips pages, use your browser's "find" or "search" option to identify particular tips you are interested in on the page, and follow up by reading the referenced web page if necessary or desired.
• The resources page lists Java performance tuning resources including books, tools, reports, other performance tuning sites of interest, and Java performance tuning discussion groups.
• The news pages are monthly newsletters listing any new Java performance tuning related information, together with Kirk Pepperdine's discussion group roundup and Javva The Hutt.
• The tool reports pages are detailed introductory reports on various Java performance related tools, for both free and commercial tools.

This site has been designed to download almost as fast as possible. (Some stylistic markup and required server-side processing has been used in preference to absolute speed contraints.) The web tree contains very few graphics and almost no complex typesetting markup except for very simple tables, and the main pages can be accessed directly from the menu.

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