Huge resident size despite small heap

[Per Liden]

As a start, you could enable native memory tracking in the JVM and see 
if that tells you anything.

$ java -XX:NativeMemoryTracking=summary ...
$ jcmd <pid> VM.native_memory

If it doesn't, I would look closer at that native library and how it's used.

cheers,
Per

On 3/27/22 23:18, Stefan Reich wrote:
> Oops, correction (sorry for spam) - these options aren't even used in 
> the process in question. It's -Xmx2g, and nothing else.
> 
> On Sun, 27 Mar 2022 at 23:17, Stefan Reich 
> <stefan.reich.maker.of.eye at googlemail.com 
> <mailto:stefan.reich.maker.of.eye at googlemail.com>> wrote:
> 
>     Quick follow-up: The only GC-related command line options I use are
> 
>        -XX:MaxHeapFreeRatio=20 -XX:MinHeapFreeRatio=10
>     -XX:+UseStringDeduplication
> 
>     On Sun, 27 Mar 2022 at 23:14, Stefan Reich
>     <stefan.reich.maker.of.eye at googlemail.com
>     <mailto:stefan.reich.maker.of.eye at googlemail.com>> wrote:
> 
>         Hi, I am currently running OpenJDK 16 on my server (will upgrade
>         to 17 when I'm sure none of my code is dependent on illegal
>         accesses). OS is Ubuntu 18.
> 
>         I am noticing that a long running server process eventually
>         (after a few days) grows enormously in its resident size. Right
>         now it is at 7 GB. Performing a GC doesn't get it any lower.
> 
>         The weird part is that the process is run with -Xmx2g, and
>         currently used heap according to java.lang.Runtime is only 400
>         MB after GC, going up to at most 1 GB in operation.
> 
>         How do these numbers fit together?
> 
>         I've seen the resident size even higher (13+ GB), and at that
>         point I noticed the process getting significantly slower too
>         (web pages taking 1-2 seconds to load instead of near instant).
> 
>         At a typical moment in time, no Java threads are running (I
>         monitor this every second).
> 
>         An obvious suspect is of course any native library loaded. The
>         only native library in use is, I think, the OSHI library.
> 
>         Any ideas why this might be happening?
> 
>         Many greetings,
>         Stefan
> 
>         -- 
>         == Gaz.AI <http://Gaz.AI> ==
> 
> 
> 
>     -- 
>     == Gaz.AI <http://Gaz.AI> ==
> 
> 
> 
> -- 
> == Gaz.AI <http://Gaz.AI> ==
> 
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