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+<div align="right"><small>
+© Copyright 2009 Contributors.
+All rights reserved.
+</small></div>
+
+<h1>AspectJ 1.6.7 Readme</h1>
+
+<p>AspectJ 1.6.7 includes some radical internal changes. These improvements enable faster compilation, faster binary weaving,
+faster load time weaving and in some situations faster generated code.</p>
+
+<h2>Pointcut timers</h2>
+<p>Until 1.6.7 there has not really been a way to determine if it is just one of your pointcuts that is hurting your weaving
+performance. In 1.6.7 it is possible to turn on timers for pointcuts. These timers show
+the time spent in the weaver matching the pointcut components against join points. The details on this feature are
+here: <a href="http://andrewclement.blogspot.com/2009/11/aspectj-profiling-pointcut-matching.html">Profiling pointcut
+matching</a>. Basically by turning on the options '-timers -verbose' on the command line (or via Ant), output will be produced
+that looks a little like this:
+
+<pre><code>
+Pointcut matching cost (total=6532ms for 675000 joinpoint match calls):
+Time:482ms (jps:#168585) matching against
+ (staticinitialization(*y*.()) && persingleton(SimpleAspect))
+Time:3970ms (jps:#168585) matching against
+ (execution(* *t*.*(*)) && persingleton(SimpleAspect))
+Time:538ms (jps:#168584) matching against
+ (execution(* *f*(..)) && persingleton(SimpleAspect))
+Time:1536ms (jps:#168584) matching against
+ (execution(* java.lang.CharSequence+.*e*(..)) && persingleton(SimpleAspect))
+Time:4ms (jps:#662) matching against
+ (within(*p*) && persingleton(SimpleAspect))
+</code></pre>
+
+<p>It shows the component, the number of joinpoints (jps) the weaver attempted to match it against and how many milliseconds were
+spent performing those matches. The options can also be turned on
+<a href="http://contraptionsforprogramming.blogspot.com/2009/11/getting-aspectj-pointcut-matching-timer.html"/>through AJDT</a>.
+Armed with this information you can optimize your pointcuts or post on the mailing list asking for help. The timers can even be
+turned on for load time weaving. </p>
+
+
+<h2>Faster matching</h2>
+
+<p>The changes to enable pointcut profiling enabled some targeted work to be done on the matching algorithms. These
+have remained unchanged for a few years, but in 1.6.7 have received a bit of an overhaul. 'Fast match' has
+been implemented for the execution() pointcut, drastically reducing weave times for heavy users of execution - more details
+<a href="http://andrewclement.blogspot.com/2009/11/aspectj-how-much-faster-is-aspectj-167.html">here</a>. The pointcut cost
+calculator (which is used to sort pointcuts to optimize matching speed) has been reviewed and after determining that
+this() ought to be considered cheaper than call() - any user combining those two pointcut designators should see an improvement
+(one users build time reduced from 38minutes to 6minutes with that change!).</p>
+
+<p>As well as faster matching there is also less exploration to determine a match. Visitors that walk hierarchies and discover
+methods now terminate as early as possible once they can determine something is a match or is definetly not a match. This reduces
+memory usage, speeds up weaving and reduces the occurrences of those annoying 'cantFindType' messages.</p>
+
+<h2>aop.xml processing</h2>
+
+<p>The processing of include/exclude entries in aop.xml has been rewritten. It now optimizes for many more common patterns. If
+a pattern is optimized then there is no need to ask the weaver to do an expensive include/exclude match. More details
+<a href="http://andrewclement.blogspot.com/2009/12/aspectj-167-and-faster-load-time.html">here</a>.
+
+<h2>Less need to tweak options for load time weaving</h2>
+
+<p>A number of options were previously configurable for load time weaving that were considered experimental. These options
+have now been tested enough in the field that they are considered fully reliable and are on by default in 1.6.7. If you have
+been using either of these:
+<ul>
+<li>typeDemotion
+<li>runMinimalMemory
+</ul>
+<p>then please delete them from your weaver options section, the weaver will now do the right thing out of the box.</p>
+
+<h2>Benchmarking memory and performance</h2>
+
+<p>All those changes above, and some additional tweaks, mean we are now using less memory than ever before and getting
+things done more quickly.</p>
+<p><a href="http://andrewclement.blogspot.com/2009/12/aspectj-167-and-faster-load-time.html">This post</a> discusses
+the details. From that article, the graph below shows the speed and memory consumption of the
+various AspectJ 1.6 releases when load time weaving a small application loading in Tomcat. For each of 10 iterations (x axis),
+the top comparison is startup time in
+milliseconds, the lower comparison is memory used in bytes.</p>
+<p><img src="167Memory.png" align="center"/></p>
+
+<h2>Annotation binding</h2>
+
+<p>All those changes affect compilation/weaving but what about the code that actually runs? One user, Oliver Hoff, raised
+a query on the performance of annotation binding. His case uncovered an old TODO left in the code a few years ago:</p>
+<code><pre>// OPTIMIZE cache result of getDeclaredMethod and getAnnotation?</pre></code>
+
+<p>Annotation binding has become a very common use case since that was written and 1.6.7 was the time TODO it.</p>
+
+<p>The result is an optimization for the general case of binding an annotation, but also support for a new bit of syntax
+that aids binding of a string annotation member value - using this latter syntax generates extremely fast code.</p>
+
+<p>Here are some numbers for a simple benchmark retrieving the annotation value at an execution join point
+in different ways. The three scenarios look like this (where the annotation type is 'Marker' and it has a String value field
+called 'message'):</p>
+
+<code><pre>
+ // CaseOne: annotation value fetching is done in the advice:
+ pointcut adviceRetrievesAnnotation(): execution(@Marker * runOne(..));
+ before(): adviceRetrievesAnnotation() {
+ Marker marker = (Marker) ((MethodSignature)
+ thisJoinPointStaticPart.getSignature()).getMethod().getAnnotation(Marker.class);
+ String s = marker.message();
+ }
+
+ // CaseTwo: annotation binding is done in the pointcut, advice retrieves message
+ pointcut pointcutBindsAnnotation(Marker l): execution(@Marker * runTwo(..)) && @annotation(l);
+ before(Marker l): pointcutBindsAnnotation(l) {
+ String s = l.message();
+ }
+
+ // CaseThree: annotation binding directly targets the message value in the annotation
+ pointcut pointcutBindsAnnotationValue(String msg):
+ execution(@Marker * runThree(..)) && @annotation(Marker(msg));
+ before(String s): pointcutBindsAnnotationValue(s) {
+ // already got the string
+ }
+</pre></code>
+
+<p>Before 1.6.7, case 2 was slower than case 1 and case 3 wasn't supported syntax. The two bugs with more info are
+<a href="https://bugs.eclipse.org/bugs/show_bug.cgi?id=296484">Bug 296484</a> and
+<a href="https://bugs.eclipse.org/bugs/show_bug.cgi?id=296501">Bug 296501</a>.</p>
+
+<p>Now this is a micro benchmark, slightly unrepresentative of the real world because the advice isn't doing anything
+else, but it does really stress the AspectJ binding code. For the benchmark numbers the join points advised by those advice
+were invoked 1,000,000 times. AspectJ 1.6.7:</p>
+
+<code><pre>
+Manually fetching annotation with getAnnotation(): 645ms
+Binding annotation with @annotation(Marker): 445ms (was >20 *seconds* for 1.6.6, due to an extra reflection call)
+Binding annotation value with @annotation(Marker(message)): 3ms
+</pre></code>
+
+<p>The new syntax is definetly the best way to bind an annotation string value.</p>
+
+<hr>
+
+<a name="bugsfixed"/>
+<h4>Bugs fixed</h4>
+<p>The complete list of issues resolved for AspectJ 1.6.7 can be found with
+this bugzilla query:
+<ul>
+<li><a href="https://bugs.eclipse.org/bugs/buglist.cgi?query_format=advanced&short_desc_type=allwordssubstr&short_desc=&product=AspectJ&target_milestone=1.6.7&long_desc_type=allwordssubstr&long_desc=&bug_file_loc_type=allwordssubstr&bug_file_loc=&status_whiteboard_type=allwordssubstr&status_whiteboard=&keywords_type=allwords&keywords=&bug_status=RESOLVED&bug_status=VERIFIED&bug_status=CLOSED&emailtype1=substring&email1=&emailtype2=substring&email2=&bugidtype=include&bug_id=&votes=&chfieldfrom=&chfieldto=Now&chfieldvalue=&cmdtype=doit&order=Reuse+same+sort+as+last+time&field0-0-0=noop&type0-0-0=noop&value0-0-0=">Bugs resolved</a>
+</ul>
+<hr>
+
+<h4>
+<!-- ============================== -->
+</body>
+</html>
projects / aspectj.git / commitdiff
