UL Viewer is log parser for JEP 158: Unified JVM Logging and JEP 271: Unified GC Logging.

$ cd ulviewer-<version>-Linux-amd64/bin
$ ./ulviewer

• Run ulviewer.bat
• If your machine has WSL (Windows Subsystem for Linux), you can run ulviewer directly.
  • ulviewer is shell script.

You can open several logs from [File] -> [Open Log] menu.

After selecting logs, Log parser wizard is shown.

You can choose log decorations for parsing. [Field value] column shows the value of decoration. You can choose decoration format on [Decoration] column. [Decoration] is ChoiceBox, so you can choose Unified JVM Logging official log decorations.

After that, you can push [OK] button.

Your logs are shown in main window.

• You can set filters through log decoration. You can choose decoration from ComboBox, and check on CheckBox.
• If you want to search logs with some keywords, you can search it through search window.
• Copy selected log entry when you press CTRL+C.

If you want to draw chart(s), you have to add tag(s) which indicates time to -Xlog option as below:

• time (t)
• utctime (utc)
• uptime (u)
• timemillis (tm)
• uptimemillis (um)
• timenanos (tn)
• uptimenanos (un)

In addition, you have to add tags (tg) to log tags.

• [Chart] -> [Memory] -> [Java heap]
• You need to open info level log (gc=info).
• You can check Java heap memory. This chart shows all STW collection (all major/minor GCs)
• You can also check specific GC events when you click the plot on the chart.

• [Chart] -> [Memory] -> [Pause time]
• You need to open info level log (gc=info).
• You can check GC STW time.
• You can also check specific GC events when you click the plot on the chart.

• [Chart] -> [Memory] -> [Metaspace]
• You need to open info level log (gc+metaspace=info).
• You can check Metaspace usage and capacity. This chart shows Metaspace GC event.

• [Chart] -> [Memory] -> [CodeCache]
• You need to open debug level log (compilation+codecache=debug).
• You can check CodeCache usage. This chart stacks CodeCache usage by segments (non-profiled nmethods, profiled nmethods, non-nmethods).

• [Chart] -> [Memory] -> [Class histogram]
• You need to open trace level log (gc+classhisto*=trace).
• You can check class histogram when Full GC is invoked.

• [Chart] -> [VM Operations]
• You need to open debug level log (vmoperation=debug).
• You can check all VM operations.

• [Table] -> [Class loading]
• You need to open debug level log for class loading, and need to open info level log for class unloading (class+load=debug,class+unload=info).
• You can check class loading / unloading information.

• [Table] -> [Age table]
• You need to open trace level log (gc+age=trace).
• You can check age table when GC is invoked.

You have to use JDK 17 or later.

$ mvn package

The GNU Lesser General Public License, version 3.0