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It's common knowledge that C, F, L, l and M of PatternLayout are slow:
WARNING Generating caller location information is extremely slow and should be avoided unless execution speed is not an issue.
Also, this book mentions that some applications can gain 10% speed only from changing the logging format.
But the question is, exactly how slow are these conversion characters?
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Layout class and overrides the format() method to structure the logging information according to a supplied pattern. PatternLayout is also a simple Layout object that provides the following-Bean Property which can be set using the configuration file: Sr.No. Property & Description.
1.2 Log4j Conversion Pattern -5p is the format modifier for the conversion character p (i.e. priority). This justifies the priority name with a minimum of 5 characters.
if it is line number you can use %L (Used to output the line number from where the logging request was issued.)
The format characters used in log4j are, L- it is used to output the line number from where the logging request was processed or issued. m- It is used to output the application supplied message related to the logging event. p- It is used to output the priority of the logging event.
I measured locally on my computer using a FileAppender. I warmed up the test nicely, measured many executions and averaged the (relatively consistent) results. The loop contained execs++;log.info("t");The exact numbers do not matter (because they depend on my computer) but proportions do. I used log4j-1.2.16.jar on Java 1.6.0_10 (Client VM).
It turns out that whenever any of the C, F, L, l or M appeared in the pattern, logging was at least 5 times slower.
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