Odd OS-level memory reporting for Java

[Vitaly Davidovich]

>
> In the case of the Linux machine, I can illustrate that there is
> definitely a reporting bug.  If you take the 48GB currently allocated to
> the disk cache, and add the *reported* 22GB resident size of the Solr
> process, you get 70GB ... but the machine only has 64GB total.


I'm not sure you can add RES and cached together.  RES includes file-backed
pages (i.e. it's not just anon pages), but those same pages may also be in
the page cache and reported in cached.

On Thu, Jan 7, 2016 at 11:15 AM, Shawn Heisey <java at elyograg.org> wrote:

> I have seen something very odd with memory reporting in both Windows and
> Linux.
>
> This may not be the correct list for this question, but I am already
> subscribed to a very large number of mailing lists and would prefer to
> not add another one for a one-off question.  I apologize if this is the
> wrong list.
>
> Take a look at these two screenshots:
>
> https://www.dropbox.com/s/64en3sar4cr1ytj/linux-solr-mem-high-shr.png?dl=0
> https://www.dropbox.com/s/w4bnrb66r16lpx1/Resource%20Monitor.png?dl=0
>
> The first one is a Linux server that I am running, the second is a
> Windows server that someone else is running.  Both machines are running
> Solr.  The Windows machine is running two copies of Solr, and the Solr
> processes are at the top of both lists.  The Linux machine has an 8GB
> heap for its copy of Solr, and I believe that each of the copies of Solr
> on the Windows machine have the heap set to 14GB.
>
> In both cases, the shared memory reported is very high, with the
> resident (or working) memory *far* higher than the configured heap size.
>
> In the case of the Linux machine, I can illustrate that there is
> definitely a reporting bug.  If you take the 48GB currently allocated to
> the disk cache, and add the *reported* 22GB resident size of the Solr
> process, you get 70GB ... but the machine only has 64GB total.
>
> On the Linux machine, Solr is accessing over 100GB of data via MMap (see
> the VIRT memory size of 121GB).  This is the data that is in the disk
> cache.  I was told that the indexes are even larger on the Windows machine.
>
> This is the Java version on the Linux machine.  I am working to learn
> what the version is on the Windows machine.
>
> java version "1.7.0_72"
> Java(TM) SE Runtime Environment (build 1.7.0_72-b14)
> Java HotSpot(TM) 64-Bit Server VM (build 24.72-b04, mixed mode)
>
> Here are the packages providing this Java version (CentOS 6.6).  I used
> the source RPM on the city-fan.org website and the official tarball from
> Oracle:
>
> java-1.7.0-oracle-jdbc-1.7.0.72-1.0.cf.x86_64
> java-1.7.0-oracle-devel-1.7.0.72-1.0.cf.x86_64
> java-1.7.0-oracle-1.7.0.72-1.0.cf.x86_64
>
> Is this memory reporting problem a bug in Java or a bug in both
> operating systems?  I do not have easy access to any other OS platforms.
>
> Thanks,
> Shawn
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