Huge resident size despite small heap

[Thomas Stüfe]

Hi Bernd,

Note that DBB usage shows up in NMT too, as "Other" category.

Cheers, Thomas

On Mon, Mar 28, 2022 at 11:12 AM Bernd Eckenfels <ecki at zusammenkunft.net>
wrote:

> Hello,
>
> You can also check Direct Memory usage of NIO DirectByteBuffer, I think
> there is a JMX bean for it.  If the number of thread stacks and the
> MetaSpace is not an issue, this (and native leak) is the only thing which
> can account for such large usage. Also you can look at the memory mappings,
> there you can at least see if it is a single region or multiple, accounting
> for the memory (/proc/pid/(s)maps).
>
> Gruss
> Bernd
>
>
> --
> http://bernd.eckenfels.net
> ------------------------------
> *Von:* hotspot-gc-use <hotspot-gc-use-retn at openjdk.java.net> im Auftrag
> von Per Liden <per.liden at oracle.com>
> *Gesendet:* Monday, March 28, 2022 10:29:04 AM
> *An:* Stefan Reich <stefan.reich.maker.of.eye at googlemail.com>;
> hotspot-gc-use at openjdk.java.net <hotspot-gc-use at openjdk.java.net>
> *Betreff:* Re: Huge resident size despite small heap
>
> 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
> <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
> <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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