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https://issues.apache.org/jira/browse/TAP5-2332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14005923#comment-14005923
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Thiago H. de Paula Figueiredo commented on TAP5-2332:
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Jochen, in this case, I said your opinion is wrong because it goes against
almost everything which was said about code optimization in the last decades.
http://c2.com/cgi/wiki?PrematureOptimization is a good starting point. See what
Donald Knuth, one of the most important people in software development
research, has to say about this: ""Programmers waste enormous amounts of time
thinking about, or worrying about, the speed of noncritical parts of their
programs, and these attempts at efficiency actually have a strong negative
impact when debugging and maintenance are considered. We should forget about
small efficiencies, say about 97% of the time: premature optimization is the
root of all evil. Yet we should not pass up our opportunities in that critical
3%."
By the way, the patch includes a change in a test. That's code that isn't used
in Tapestry in runtime at all. It's not even included in the JAR. So this was a
completely wasted effort in optimization. AbstractOptionModel.toString() is
another one. The change in MessageConstraintsGenerator may actually be a
serious bug, but I couldn't check yet. We need to optimize hotspots, the 3%
mentioned by Knuth, and leave the rest alone.
> Optimize String concatenation performance
> -----------------------------------------
>
> Key: TAP5-2332
> URL: https://issues.apache.org/jira/browse/TAP5-2332
> Project: Tapestry 5
> Issue Type: Improvement
> Reporter: Michael Mikhulya
> Assignee: Jochen Kemnade
> Priority: Minor
> Labels: performance
> Attachments: 0001-TAP5-2332-get-rid-of-String.format-usage.patch,
> profile-patched.png, profile-vanilla.png
>
>
> During profiling I found that String.format provides much load on CPU.
> In many cases in Tapestry String.format can be easily replaced with simple
> String concatenation.
> Simple JMH (http://openjdk.java.net/projects/code-tools/jmh/) test
> {code:java}
> public class FormatVsConcat {
> private static final String format = "This is a test string with %s";
> private static final String concat1 = "This is a test string with ";
> private static final String concat2 = "test word";
> @GenerateMicroBenchmark
> public String format() {
> return String.format(format, concat2);
> }
> @GenerateMicroBenchmark
> public String concat() {
> return concat1 + concat2;
> }
> }
> {code}
> shows, that concatenation is 366(!) times faster.
> I removed only hot places in tapestry and get following results with apache
> benchmark:
> *Not patched* tapestry version:
> Requests per second: *21.38 /sec* (mean)
> Time per request: *46.764 [ms]* (mean)
> *Patched* tapestry version:
> Requests per second: *27.77 /sec* (mean)
> Time per request: *36.013 [ms]* (mean)
> So we gained 10ms per request or 20% of rendering time.
> If you don't mind I would like to get rid of String.format in all places of
> Tapestry and provide patch. I fixed only hot places which appeared during
> ab-profiling of one concrete page. So it is very likely that not all hot
> places were found and fixed.
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