The table below shows some examples of logs produced by the current (2015-11-13) prototype for JEP 271. For comparison logs with -XX:+PrintGC and -XX:+PrintGCDetails is also provided. It is intended that -Xlog:gc should be similar to -XX:+PrintGC and that -Xlog:gc* should be similar to -XX:+PrintGCDetails.
There is also a run with -XX:+PrintAdaptiveSizePolicy included. This has been replaced by logging on the "ergo" tag.
The logging provided by JEP 271 is much more flexible in its configuration options than the old logging. So, there are many more configurations that can be used to produce logs and control the output. These are just examples and hopefully they show the intent well enough to give an overview.
The previous versions with example logs and some more explanations are available here:
pre-review.00 2015-10-26
pre-review.01 2015-11-06