Solr JVM Memory settings

[Sourav Moitra <so...@gmail.com>]

Hello,

We have a Solr server with 8gb of memory. We are using solr in cloud
mode, solr version is 7.5, Java version is Oracle Java 9 and settings
for Xmx and Xms value is 2g but we are observing that the RAM getting
used to 98% when doing indexing.

How can I ensure that SolrCloud doesn't use more than N GB of memory ?

Sourav Moitra
https://souravmoitra.com

Re: Solr JVM Memory settings

[Hendrik Haddorp <he...@gmx.net>]

Beside the heap the JVM has other memory areas, like the metaspace: 
https://docs.oracle.com/javase/9/tools/java.htm
-> MaxMetaspaceSize
search for "size" in that document and you'll find tons of further 
settings. I have not tried out Oracle Java 9 yet.

regards,
Hendrik

On 11.10.2018 06:08, Sourav Moitra wrote:
> Hello,
>
> We have a Solr server with 8gb of memory. We are using solr in cloud
> mode, solr version is 7.5, Java version is Oracle Java 9 and settings
> for Xmx and Xms value is 2g but we are observing that the RAM getting
> used to 98% when doing indexing.
>
> How can I ensure that SolrCloud doesn't use more than N GB of memory ?
>
> Sourav Moitra
> https://souravmoitra.com

Re: Solr JVM Memory settings

[Hendrik Haddorp <he...@gmx.net>]

I wasn't stating that Docker is the solution at all. I was also stating 
that the native memory would go down if you limit the heap.
I'm running Solr in Docker with a memory limit and thus have to make 
sure that the memory is limited as otherwise Linux kills the JVM. For 
that I'm limiting the heap and meta space, which is also ofter refered 
as native memory. For the Oracle JVM (version 8) the heap and meta space 
can be limited. There are a few more memory areas, which I believe you 
can not limit correctly. Just putting Solr in Docker will of course not 
do any of that for you.

On 12.10.2018 19:59, Christopher Schultz wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
> Hendrik,
>
> On 10/12/18 02:36, Hendrik Haddorp wrote:
>> Those constraints can be easily set if you are using Docker. The
>> problem is however that at least up to Oracle Java 8, and I believe
>> quite a bit further, the JVM is not at all aware about those
>> limits. That's why when running Solr in Docker you really need to
>> make sure that you set the memory limits lower. I usually set the
>> heap and metaspace size. How you set them depends again a bit on
>> your Solr configuration. I prefer the JVM to crash due to memory
>> limits rather then the Linux OOM Killer killing the JVM as the
>> OutOfMemoryError from the JVM does at least state what memory was
>> out.
> Limiting the native memory used by attempting to limit the heap is not
> actually limiting the native memory used. It's just an attempt to do
> so. If you limit the native memory using OS limits (or, using Docker,
> simply make it look like there is less system memory) then you haven't
> actually achieved anything. You could have done that simply by
> lowering heap values and avoided the complexity of Docker, etc.
>
> - -chris
>
>> On 11.10.2018 16:45, Christopher Schultz wrote: Shawn,
>>
>> On 10/11/18 12:54 AM, Shawn Heisey wrote:
>>>>> On 10/10/2018 10:08 PM, Sourav Moitra wrote:
>>>>>> We have a Solr server with 8gb of memory. We are using solr
>>>>>> in cloud mode, solr version is 7.5, Java version is Oracle
>>>>>> Java 9 and settings for Xmx and Xms value is 2g but we are
>>>>>> observing that the RAM getting used to 98% when doing
>>>>>> indexing.
>>>>>>
>>>>>> How can I ensure that SolrCloud doesn't use more than N GB
>>>>>> of memory ?
>>>>> Where precisely are you seeing the 98% usage?  It is
>>>>> completely normal for a modern operating system to report
>>>>> that almost all the system memory is in use, at least after
>>>>> the system has been shuffling a lot of data.  All modern
>>>>> operating systems will use memory that has not been
>>>>> specifically allocated to programs for disk caching purposes,
>>>>> and system information tools will generally indicate that
>>>>> this memory is in use, even though it can be instantly
>>>>> claimed by any program that requests it.
>>>>>
>>>>> https://en.wikipedia.org/wiki/Page_cache
>>>>>
>>>>> If you tell a Java program that it is limited to a 2GB heap,
>>>>> then that program will never use more than 2GB, plus a little
>>>>> extra for the java runtime itself.  I cannot give you an
>>>>> exact figure for that little bit extra.  But every bit of
>>>>> data on disk that Solr accesses will end up (at least
>>>>> temporarily) in the operating system's disk cache -- using
>>>>> that unallocated memory.
>>>>>
>>>>> https://wiki.apache.org/solr/SolrPerformanceProblems#RAM
>> To be fair, the JVM can use *much more* memory than you have
>> specified for your Java heap. It's just that the Java heap itself
>> wont exceed those values.
>>
>> The JVM uses quite a bit of native memory which isn't counted in
>> the Java heap. There is only one way I know of to control that, and
>> it's to set a process-limit at the OS level on the amount of
>> memory allowed. I'm not sure how sensitive to those limits the JVM
>> actually is, so attempting to artificially constrain the JVM might
>> end up with a native OOM crash.
>>
>> -chris
>>
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Re: Solr JVM Memory settings

[Christopher Schultz <ch...@christopherschultz.net>]

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Hash: SHA256

Hendrik,

On 10/12/18 02:36, Hendrik Haddorp wrote:
> Those constraints can be easily set if you are using Docker. The
> problem is however that at least up to Oracle Java 8, and I believe
> quite a bit further, the JVM is not at all aware about those
> limits. That's why when running Solr in Docker you really need to
> make sure that you set the memory limits lower. I usually set the
> heap and metaspace size. How you set them depends again a bit on
> your Solr configuration. I prefer the JVM to crash due to memory
> limits rather then the Linux OOM Killer killing the JVM as the
> OutOfMemoryError from the JVM does at least state what memory was
> out.

Limiting the native memory used by attempting to limit the heap is not
actually limiting the native memory used. It's just an attempt to do
so. If you limit the native memory using OS limits (or, using Docker,
simply make it look like there is less system memory) then you haven't
actually achieved anything. You could have done that simply by
lowering heap values and avoided the complexity of Docker, etc.

- -chris

> On 11.10.2018 16:45, Christopher Schultz wrote: Shawn,
> 
> On 10/11/18 12:54 AM, Shawn Heisey wrote:
>>>> On 10/10/2018 10:08 PM, Sourav Moitra wrote:
>>>>> We have a Solr server with 8gb of memory. We are using solr
>>>>> in cloud mode, solr version is 7.5, Java version is Oracle
>>>>> Java 9 and settings for Xmx and Xms value is 2g but we are
>>>>> observing that the RAM getting used to 98% when doing
>>>>> indexing.
>>>>> 
>>>>> How can I ensure that SolrCloud doesn't use more than N GB
>>>>> of memory ?
>>>> Where precisely are you seeing the 98% usage?  It is
>>>> completely normal for a modern operating system to report
>>>> that almost all the system memory is in use, at least after
>>>> the system has been shuffling a lot of data.  All modern
>>>> operating systems will use memory that has not been
>>>> specifically allocated to programs for disk caching purposes,
>>>> and system information tools will generally indicate that
>>>> this memory is in use, even though it can be instantly
>>>> claimed by any program that requests it.
>>>> 
>>>> https://en.wikipedia.org/wiki/Page_cache
>>>> 
>>>> If you tell a Java program that it is limited to a 2GB heap,
>>>> then that program will never use more than 2GB, plus a little
>>>> extra for the java runtime itself.  I cannot give you an
>>>> exact figure for that little bit extra.  But every bit of
>>>> data on disk that Solr accesses will end up (at least
>>>> temporarily) in the operating system's disk cache -- using
>>>> that unallocated memory.
>>>> 
>>>> https://wiki.apache.org/solr/SolrPerformanceProblems#RAM
> To be fair, the JVM can use *much more* memory than you have
> specified for your Java heap. It's just that the Java heap itself
> wont exceed those values.
> 
> The JVM uses quite a bit of native memory which isn't counted in
> the Java heap. There is only one way I know of to control that, and
> it's to set a process-limit at the OS level on the amount of
> memory allowed. I'm not sure how sensitive to those limits the JVM
> actually is, so attempting to artificially constrain the JVM might
> end up with a native OOM crash.
> 
> -chris
> 
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Re: Solr JVM Memory settings

[Hendrik Haddorp <he...@gmx.net>]

Those constraints can be easily set if you are using Docker. The problem 
is however that at least up to Oracle Java 8, and I believe quite a bit 
further, the JVM is not at all aware about those limits. That's why when 
running Solr in Docker you really need to make sure that you set the 
memory limits lower. I usually set the heap and metaspace size. How you 
set them depends again a bit on your Solr configuration. I prefer the 
JVM to crash due to memory limits rather then the Linux OOM Killer 
killing the JVM as the OutOfMemoryError from the JVM does at least state 
what memory was out.

Hendrik

On 11.10.2018 16:45, Christopher Schultz wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
> Shawn,
>
> On 10/11/18 12:54 AM, Shawn Heisey wrote:
>> On 10/10/2018 10:08 PM, Sourav Moitra wrote:
>>> We have a Solr server with 8gb of memory. We are using solr in
>>> cloud mode, solr version is 7.5, Java version is Oracle Java 9
>>> and settings for Xmx and Xms value is 2g but we are observing
>>> that the RAM getting used to 98% when doing indexing.
>>>
>>> How can I ensure that SolrCloud doesn't use more than N GB of
>>> memory ?
>> Where precisely are you seeing the 98% usage?  It is completely
>> normal for a modern operating system to report that almost all the
>> system memory is in use, at least after the system has been
>> shuffling a lot of data.  All modern operating systems will use
>> memory that has not been specifically allocated to programs for
>> disk caching purposes, and system information tools will generally
>> indicate that this memory is in use, even though it can be
>> instantly claimed by any program that requests it.
>>
>> https://en.wikipedia.org/wiki/Page_cache
>>
>> If you tell a Java program that it is limited to a 2GB heap, then
>> that program will never use more than 2GB, plus a little extra for
>> the java runtime itself.  I cannot give you an exact figure for
>> that little bit extra.  But every bit of data on disk that Solr
>> accesses will end up (at least temporarily) in the operating
>> system's disk cache -- using that unallocated memory.
>>
>> https://wiki.apache.org/solr/SolrPerformanceProblems#RAM
> To be fair, the JVM can use *much more* memory than you have specified
> for your Java heap. It's just that the Java heap itself wont exceed
> those values.
>
> The JVM uses quite a bit of native memory which isn't counted in the
> Java heap. There is only one way I know of to control that, and it's
> to set a process-limit at the OS level on the amount of memory
> allowed. I'm not sure how sensitive to those limits the JVM actually
> is, so attempting to artificially constrain the JVM might end up with
> a native OOM crash.
>
> - -chris
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Re: Solr JVM Memory settings

[Christopher Schultz <ch...@christopherschultz.net>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Shawn,

On 10/11/18 12:54 AM, Shawn Heisey wrote:
> On 10/10/2018 10:08 PM, Sourav Moitra wrote:
>> We have a Solr server with 8gb of memory. We are using solr in
>> cloud mode, solr version is 7.5, Java version is Oracle Java 9
>> and settings for Xmx and Xms value is 2g but we are observing
>> that the RAM getting used to 98% when doing indexing.
>> 
>> How can I ensure that SolrCloud doesn't use more than N GB of
>> memory ?
> 
> Where precisely are you seeing the 98% usage?  It is completely
> normal for a modern operating system to report that almost all the
> system memory is in use, at least after the system has been
> shuffling a lot of data.  All modern operating systems will use
> memory that has not been specifically allocated to programs for
> disk caching purposes, and system information tools will generally
> indicate that this memory is in use, even though it can be
> instantly claimed by any program that requests it.
> 
> https://en.wikipedia.org/wiki/Page_cache
> 
> If you tell a Java program that it is limited to a 2GB heap, then
> that program will never use more than 2GB, plus a little extra for
> the java runtime itself.  I cannot give you an exact figure for
> that little bit extra.  But every bit of data on disk that Solr
> accesses will end up (at least temporarily) in the operating
> system's disk cache -- using that unallocated memory.
> 
> https://wiki.apache.org/solr/SolrPerformanceProblems#RAM

To be fair, the JVM can use *much more* memory than you have specified
for your Java heap. It's just that the Java heap itself wont exceed
those values.

The JVM uses quite a bit of native memory which isn't counted in the
Java heap. There is only one way I know of to control that, and it's
to set a process-limit at the OS level on the amount of memory
allowed. I'm not sure how sensitive to those limits the JVM actually
is, so attempting to artificially constrain the JVM might end up with
a native OOM crash.

- -chris
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Re: Solr JVM Memory settings

[Shawn Heisey <ap...@elyograg.org>]

On 10/10/2018 11:33 PM, Sourav Moitra wrote:
> Hello Shawn,
>
> Thanks for quick reply.
>>> Where precisely are you seeing the 98% usage?
> On the Solr web UI. Although the same Solr UI is reporting heap usage
> to be below 1 GB.
> Also I found that Solr Java is holding(VIRT) 8GB of total memory even
> with Xmx set to 2g using top command.

On the "top" screen, you can see how much memory the process is using by 
subtracting the value in the SHR column from the value in the RES column.

The VIRT column does not indicate actual memory usage.  It tells you how 
much *VIRTUAL* memory the process has allocated within the processor's 
memory mapping system.  Usually, most of this value is *not* consuming 
actual RAM.

Here's a screenshot of a "top" running on a Solr system with over 700GB 
of index data:

https://www.dropbox.com/s/85h1weuopa643za/bigindy5-top-small-shr.png?dl=0

The VIRT column says over three quarters of a terabyte ... but the 
system has only 64GB of memory, 28GB of which is allocated to the Solr 
heap.  I can guarantee you that when this screenshot was taken, the 
system was NOT having memory problems.  If the VIRT column indicated 
actual memory consumption, that would be a completely impossible 
situation -- the machine doesn't HAVE that much memory!

Additional reading on the topic of virtual memory as it relates to 
Lucene/Solr:

http://blog.thetaphi.de/2012/07/use-lucenes-mmapdirectory-on-64bit.html

On your system, I can pretty much guarantee that Solr is **NOT** 
consuming 8GB of memory.  It is consuming the 2GB you told it that it 
could have, plus a little bit extra.  If you don't have any other 
sizable programs running on this system, then the rest of your memory is 
being used by the OS -- and if you were to start another program that 
wanted a large chunk of memory, the OS would instantly and willingly 
give up some or all of its disk cache and allow that program to have the 
memory.

Thanks,
Shawn

Re: Solr JVM Memory settings

[Sourav Moitra <so...@gmail.com>]

Hello Shawn,

Thanks for quick reply.
> > Where precisely are you seeing the 98% usage?
On the Solr web UI. Although the same Solr UI is reporting heap usage
to be below 1 GB.
Also I found that Solr Java is holding(VIRT) 8GB of total memory even
with Xmx set to 2g using top command.

Can it be due to GC not clearing up the memory ?

Sourav Moitra
https://souravmoitra.com
On Thu, Oct 11, 2018 at 10:24 AM Shawn Heisey <ap...@elyograg.org> wrote:
>
> On 10/10/2018 10:08 PM, Sourav Moitra wrote:
> > We have a Solr server with 8gb of memory. We are using solr in cloud
> > mode, solr version is 7.5, Java version is Oracle Java 9 and settings
> > for Xmx and Xms value is 2g but we are observing that the RAM getting
> > used to 98% when doing indexing.
> >
> > How can I ensure that SolrCloud doesn't use more than N GB of memory ?
>
> Where precisely are you seeing the 98% usage?  It is completely normal
> for a modern operating system to report that almost all the system
> memory is in use, at least after the system has been shuffling a lot of
> data.  All modern operating systems will use memory that has not been
> specifically allocated to programs for disk caching purposes, and system
> information tools will generally indicate that this memory is in use,
> even though it can be instantly claimed by any program that requests it.
>
> https://en.wikipedia.org/wiki/Page_cache
>
> If you tell a Java program that it is limited to a 2GB heap, then that
> program will never use more than 2GB, plus a little extra for the java
> runtime itself.  I cannot give you an exact figure for that little bit
> extra.  But every bit of data on disk that Solr accesses will end up (at
> least temporarily) in the operating system's disk cache -- using that
> unallocated memory.
>
> https://wiki.apache.org/solr/SolrPerformanceProblems#RAM
>
> Thanks,
> Shawn
>

Re: Solr JVM Memory settings

[Shawn Heisey <ap...@elyograg.org>]

On 10/10/2018 10:08 PM, Sourav Moitra wrote:
> We have a Solr server with 8gb of memory. We are using solr in cloud
> mode, solr version is 7.5, Java version is Oracle Java 9 and settings
> for Xmx and Xms value is 2g but we are observing that the RAM getting
> used to 98% when doing indexing.
>
> How can I ensure that SolrCloud doesn't use more than N GB of memory ?

Where precisely are you seeing the 98% usage?  It is completely normal 
for a modern operating system to report that almost all the system 
memory is in use, at least after the system has been shuffling a lot of 
data.  All modern operating systems will use memory that has not been 
specifically allocated to programs for disk caching purposes, and system 
information tools will generally indicate that this memory is in use, 
even though it can be instantly claimed by any program that requests it.

https://en.wikipedia.org/wiki/Page_cache

If you tell a Java program that it is limited to a 2GB heap, then that 
program will never use more than 2GB, plus a little extra for the java 
runtime itself.  I cannot give you an exact figure for that little bit 
extra.  But every bit of data on disk that Solr accesses will end up (at 
least temporarily) in the operating system's disk cache -- using that 
unallocated memory.

https://wiki.apache.org/solr/SolrPerformanceProblems#RAM

Thanks,
Shawn

Re: Solr JVM Memory settings

[Terry Steichen <te...@net-frame.com>]

Don't know if this directly affects what you're trying to do.  But I
have an 8GB server and when I run "solr status" I can see what % of the
automatic memory allocation is being used.  As it turned out, solr would
occasionally exceed that (and crashed). 

I then began starting solr with the additional parameter: "-m 1g"  Now
the solr consumption is almost always 50% or less, and have had no
further problems.


On 10/11/2018 12:08 AM, Sourav Moitra wrote:
> Hello,
>
> We have a Solr server with 8gb of memory. We are using solr in cloud
> mode, solr version is 7.5, Java version is Oracle Java 9 and settings
> for Xmx and Xms value is 2g but we are observing that the RAM getting
> used to 98% when doing indexing.
>
> How can I ensure that SolrCloud doesn't use more than N GB of memory ?
>
> Sourav Moitra
> https://souravmoitra.com
>