目标中的-T10C和-T4C -am是什么意思

Question

我想知道 -T4C 和 -T10C 之间的区别以及这多个内核将如何影响构建时间。

Answer 1

The help output of Maven via mvn --help will print out the following for -T :

 -T,--threads <arg>                     Thread count, for instance 2.0C
                                        where C is core multiplied

The first part of the answer to that is:

If you have for example a machine which has 5 cores it will run your build with 4 * 5 threads (in case of -T4C ) which means 20 threads in total. Or assuming you have given -T10C results in 10 * 5 which means 50 threads.

So far the theory.

The first thing is you have to have a multi module build which contains a number of modules. Based on the dependencies between the modules you could decrease your buildtime by using something like mvn clean verify -T3 but that dependends on the number of modules and their dependencies between each other. In general the more modules you have the more you decrease the buildtime but that highly depends on the dependency structure of your modules.

In a single module build this will usually not descrease the build time. It can descrease the whole build time dependending how your unit tests/integration test setup is done and how many unit- and/or integration tests you have.

So the rule of thumb is simply to try to build your whole project with -T3 and check if your buildtime descreases if so next time try to use -T6 (assuming you have enough cores)...

Only if you have a very large number of modules (100+) you can try with higher numbers if you like...

So most of the times you can simply try to build with mvn -T1C that means the same number of threads as the number of CPU cores you have ...

In the end it depends on the number of modules you have and the relationship between the modules...

You need to measure the build times with each different parameter of -TXXX to find the most performant way..