Re: tune CSS Phoebus's memory usage

["Kasemir, Kay via Tech-talk" <tech-talk at aps.anl.gov>]

I’d be concerned about memory leaks, but not memory usage in general.

 

Java Virtual Machine Memory

---------------------------

 

CS-Studio/Phoebus is a plain Java application, with memory managed by the JVM.

See also https://developers.redhat.com/articles/2021/09/09/how-jvm-uses-and-allocates-memory

 

When you launch the applications, the JVM option `-Xmx` sets the maximum amount of memory that the JVM will use, and `-Xms` sets the initial amount.

 

For example,

 

```

export JDK_JAVA_OPTIONS="-Xms500M -Xmx2G"

java -jar product.jar

```

 

will start the JVM will 500MB of memory, and it will allocate up to 2GB.

 

A tool like VisualVM (free, https://visualvm.github.io) or JProfiler (very good but not free, https://www.ej-technologies.com/products/jprofiler/overview.html) can be used to track memory usage over time.

 

What you should see is a sawtooth-type pattern where the application uses more and more memory, maybe up to the `-Xmx` limit, then frees it.

When you open several displays, the sawtooth pattern may ramp up more rapidly, and when you then close those displays, it should free memory and return to a slower/longer sawtooth pattern. If you find a scenario where the memory keeps increasing until running out of memory, you may have spotted a memory leak that should should report, ideally with a reproducible recipe.

 

 

Linux Memory

------------

 

It can be confusing to compare memory usage as reported by the JVM with the memory usage reported by the Linux OS.

Especially the "VIRT" virtual memory indicated in for example `top` may appear huge, but that tends to have no

practical significance, see for example https://stackoverflow.com/questions/561245/virtual-memory-usage-from-java-under-linux-too-much-memory-used, which also points to related discussions of the glibc `MALLOC_ARENA_MAX` setting.

 

 

 

 

From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Xiao, Lingran via Tech-talk <tech-talk at aps.anl.gov>
Date: Monday, July 29, 2024 at 1:51 PM
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: [EXTERNAL] tune CSS Phoebus's memory usage

Hi all,

 

We're concerned about CSS Phoebus's high memory usages. I was wondering do you have the same concerns. And did you take any actions to minimize the memory usages while maintaining Phoebus's performance? Any inputs are welcome.

 

Thanks a lot,

Lingran