Latest news

NEW: 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"

APRIL NEWSLETTER

• We list all the latest Java performance related news and articles
  • "If you're storing ints into a HashMap, they're being converted to and from Integers (either explicitly or through autoboxing). Changing the code to use the appropriate trove map (TObjectIntHashMap, TIntObjectHashMap or TIntIntHashMap) gives you a smaller, faster, and higher throughput implementation, at almost no effort"
• All the latest Java performance tips extracted in concise form
  • "You can auto-tune a system if you have a parameter which can be adjusted that you can control, a measure that the parameter affects, and a target for that measure (and assuming the parameter and measure react within reasonable times). Then using a controller with a feedback loop, the parameter can be auto-adjusted to minimize deviations from the target. This can allow your system to adapt to dynamically changing resource contention (eg request surges)"

MARCH NEWSLETTER

• We list all the latest Java performance related news and articles
  • "In the performance world, we always go for the 'fail fast' implementation - as with any collection comparison, you compare subsets of the collection, and fail as soon as you know any subset does not equate. But in the security world, this can be dangerous."
• All the latest Java performance tips extracted in concise form
  • "If you need extremely low latencies, you have to take account of the mode and route of physical transmission of signals as well as the transport layer. Fibre transmits at 2/3 the speed of light, and most fibre routes tested were 1.5-2 times longer than the shortest physical path, so a typical good fibre route is already ~3x slower than maximum possible. DNS lookup and TCP handshakes imply further large overheads"

FEBRUARY NEWSLETTER

• We list all the latest Java performance related news and articles
  • "I list the pros and cons of microservices"
• All the latest Java performance tips extracted in concise form
  • "Concurrent access techniques in order of increasing throughput are: a lock; lock striping; splitting data structure to split writes; commit logging with asynchronous batched updates. "

JANUARY NEWSLETTER

• We list all the latest Java performance related news and articles
  • "We've had software transactional memory in Java for 20 years in at least one system"
• All the latest Java performance tips extracted in concise form
  • "In general you should size a JVM system based on heap allocation, not CPU allocation"

DECEMBER NEWSLETTER

• We list all the latest Java performance related news and articles
  • "99.99% means you have less than an hour's total downtime over the whole year (8760 hours)"
• All the latest Java performance tips extracted in concise form
  • "Soft references are collected much less eagerly than weak ones, typically in response to memory pressure (weakly referenced objects could be collected at any time). This means a double hit happens when memory pressure increases, with the GC already trying hard to free up memory it also starts to look at softly referenced objects meaning even longer or more frequent GCs"

NOVEMBER NEWSLETTER

• We list all the latest Java performance related news and articles
  • "where to actually focus your effort: on enabling the architecture to scale horizontally and specifically handling the interactions between the components"
• All the latest Java performance tips extracted in concise form
  • "Choice of protocol for IoT depends on how and what pattern of communications the devices need to do - device processing capability, interoperability, message sizes, communication encryption, reliability of message delivery (atmost once, at least once, exactly once), and communication flow control (importantly whether you need to ensure there is a control channel open which means you can't allow congested channels) all need to factor in to the protocol decision"

OCTOBER NEWSLETTER

• We list all the latest Java performance related news and articles
  • "the clear implication for JVMs: memory access is going to become the bottleneck in CPU processing"
• All the latest Java performance tips extracted in concise form
  • "Put limits on everything: bound queues; timeout remote calls; terminate idle connections; kill long (db) queries; etc." and "For stateful services in a service instance, cache data and have the client talk to the same instance (use sticky sessions). "

SEPTEMBER NEWSLETTER

• We list all the latest Java performance related news and articles
  • "In Java 9, these combinations will cause a startup error instead of the deprecated message, aborting JVM startup"
• All the latest Java performance tips extracted in concise form
  • "The compare-and-swap (CAS) loop is a pattern used in many lock-free data structures. If another thread modifies the shared memory and changes it back before the first thread resumes execution (the ABA problem), a CAS can incorrectly succeed"

AUGUST NEWSLETTER

• We list all the latest Java performance related news and articles
  • "'-Xrun' is a generic command to the JVM to run a shared library agent given by the name of the subsequent characters, ie '-Xrunxyz' would run the shared library agent 'xyz'; on unix there will be a 'libxyz.so', on windows a 'xyz.dll'"
• All the latest Java performance tips extracted in concise form
  • "For more efficient debugging of asynchronous calls, either pass the stacks as you move from one context to the next, or more efficiently generate a UUID at the start and pass the UUID across all asynchronous contexts (and log that UUID) so that you can track a request across asynchronous processing using the UUID"

JULY NEWSLETTER

• We list all the latest Java performance related news and articles
  • "A tiny change in Java 8 is that Thread.stop(Throwable) is now disabled - it now throws an UnsupportedOperationException instead of working as it did in earlier Java versions. Thread.stop() still works (ie the stop() call with no argument)"
• All the latest Java performance tips extracted in concise form
  • "Make sure everything is getting JIT compiled. A quick technique to check this is to switch on the -XX:+PrintCompilation flag, then redo with -XX:ReservedCodeCacheSize doubled and if more methods are getting compiled the second time, the code cache was too small"

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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