vm-memory | Virtual machine 's guest memory crate | Emulator library
kandi X-RAY | vm-memory Summary
kandi X-RAY | vm-memory Summary
Virtual machine's guest memory crate
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QUESTION
I tried to check the memory consumption of a program. During the check, I have noticed some interesting things.
I created a Load class, which contains some fields.
...ANSWER
Answered 2021-Feb-24 at 20:31The largest
primitive
can hold8 bytes
.every Object has at least
12 bytes
(with default 64 bit VMs and relatively small heap) of headers. Automatically making it bigger than a primitive.
There is a single good library that I am aware of that does correctly, called jol
. here is a related question.
It is rather easy to get jol
set-up and run the samples to understand the actual numbers you are interested in.
QUESTION
The JVM Memory Pressure of my AWS Elasticsearch cluster has been increasing consistently. The pattern I see for the last 3 days is that it adds 1.1% every 1 hour. This is for one of the 3 master nodes I have provisioned.
All other metrics seem to be in the normal range. The CPU is under 10% and there are barely any indexing or search operations being performed.
I have tried clearing the cache for fielddata
for all indices as mentioned in this document but that has not helped.
Can anyone help me understand what might be the reason for this?
...ANSWER
Answered 2020-Aug-24 at 15:02Got this answer from AWS Support
I checked the particular metric and can also see the JVM increasing from the last few days. However, I do not think this is an issue as JVM is expected to increase over time. Also, the garbage collection in ES runs once the JVM reaches 75% (currently its around 69%), after which you would see a drop in the JVM metric of your cluster. If JVM is being continuously > 75 % and not coming down after GC's is a problem and should be investigated.
The other thing which you mentioned about clearing the cache for fielddata for all indices was not helping in reducing JVM, that is because the dedicated master nodes do not hold any indices data and their related caches. Clearing caches should help in reducing JVM on the data nodes.
QUESTION
Java 10 introduced the corresponding -XX:{Initial|Min|Max}RAMPercentage
flags to configure heap in container environment.
I'm running Elasticsearch in a k8s cluster. The Elaticsearch container has the following resources configuration:
...ANSWER
Answered 2020-Dec-06 at 12:31In a container, MaxRAMPercentage
is calculated basing on cgroup memory.limit_in_bytes
value.
It is limits
Kubernetes configuration that affects cgroup memory limit. So, in your case, the maximum heap size will be set to 256M (50% of the limit).
QUESTION
I'm working with OpenJDK 11 and a very simple SpringBoot application that almost the only thing it has is the SpringBoot actuator enabled so I can call /actuator/health etc.
I also have a kubernetes cluster on GCE very simple with just a pod with a container (containing this app of course)
My configuration has some key points that I want to highlight, it has some requirements and limits
...ANSWER
Answered 2019-Mar-03 at 10:42I finally found my issue and I want to share it so others can benefit in some way from this.
As I found on my last edit I had a thread problem that was causing all the memory consumption over time, specifically we was using an asynchronous method from a third party library without properly taking care those resources (ensure those calls was ending correctly in this case).
I was able to detect the issue because I used a memory limit on my kubernete deployment from the beginning (which is a good practice on production environments) and then I monitored very closely my app memory consumption using tools like jstat, jcmd, visualvm, kill -3
and most importantly the -XX:NativeMemoryTracking=summary
flag that gave me so much detail in this regard.
QUESTION
I'm reading about the Java Compressed OOPS. I see that what Java does is a lot of shifting to use compressed pointers for all their object references.
What I can understand is that with a large number of objects, going from -XX:+UseCompressedOops
to -XX:-UseCompressedOops
, you may end up using a lot more memory.
Say you have 1 million objects, in the first case, you need 4Mb of data for references, in the second case, you need 8Mb.
Now, I have a computer with 64Gb of RAM and wanted to use some 50Gb for Cassandra. But now I'm wondering whether the extra 18Gb will really help or will it be filled up with many useless pointer data.
So my question is:
Does Cassandra manages a ton of small objects, or does it instead manage only a few large objects? (i.e. Does it allocate a separate buffer for each cell, each row, one buffer per sstable?)
In the first case, we may not gain much when going over 32Gb of Cassandra cache vs 50Gb.
...ANSWER
Answered 2019-Jan-04 at 09:43This is what one of my cluster nodes looks like from heap perspective:
QUESTION
I needed to get the throughput of Heron Cluster for some reasons, but there is no metric in the Heron UI. So do you have any ideas about how to monitor the throughput of Heron Cluster? Thanks.
The result of running heron-explorer as follows:
...ANSWER
Answered 2018-Aug-03 at 08:52You can use the execute-count
of you sink component to measure the output of your topology. If each of your components have a 1:1 input:output ratio then this will be your throughput.
However, if you are windowing tuples into batches or splitting tuples (like separating sentences into individual words) then things get a little more complicated. You can get the input into your topology by looking at the emit-count
of your spout components. You could then use this in comparison to you bolt execute-counts
to create your own throughput metric.
An easy way to get programmatic access to these metrics is via the Heron Tracker REST API. You can use your chosen language's HTTP library (like Requests for Python) to query the last 3 hours of data for a running topology. If you require more than 3 hours of data (the maximum stored by the topology TMaster) you will need to use one of the other metrics sinks to send metrics to an external database. Heron currently provides sinks for saving to local files, Graphite or Prometheus. InfluxDB support is in the works.
QUESTION
I'm new to byte code so I've been looking at examples online of Java code and its byte code conversions. My confusion lies with the incrementation pattern of the instruction number. For example, refer to a byte code snippet from https://salilsurendran.wordpress.com/2015/01/01/jvm-memory-barriers/:
...ANSWER
Answered 2018-Mar-29 at 23:44It's not an 'instruction number'. It is an instruction address, and it is incremented by the length of the previous instruction.
QUESTION
I have an Apache Solr 4.2.1 instance that has 4 cores of total size (625MB + 30MB + 20GB + 300MB) 21 GB.
It runs on a 4 Core CPU, 16GB RAM, 120GB HD, CentOS dedicated machine.
1st core is fully imported once a day.
2nd core is fully imported every two hours.
3rd core is delta imported every two hours.
4rth core is fully imported every two hours.
The server also has a decent amount of queries (search for and create, update and delete documents).
Every core has maxDocs: 100 and maxTime: 15000 for autoCommint and maxTime: 1000 for autoSoftCommit.
The System usage is:
Around 97% of 14.96 GB Physical Memory
0MB Swap Space
Around 94% of 4096 File Descriptor Count
From 60% to 90% of 1.21GB of JVM-Memory.
When I reboot the machine the File Descriptor Count fall to near 0 and then steadily over the course of on week or so it reaches the aforementioned value.
So, to conclude, my questions are:
Is 94% of 4096 File Descriptor Count normal?
How can I increase the maximum File Descriptor Count?
How can I calculate the theoretical optimal value for the maximum and used File Descriptor Count.
Will the File Descriptor Count reaches 100? If yes, the server will crash? Or it will keep it bellow 100% by itself and functions as it should?
Thanks a lot beforehand!
...ANSWER
Answered 2017-Oct-05 at 20:25- Sure.
ulimit -n
. See Increasing ulimit on CentOS.- There really isn't one - as many as needed depending on a lot of factors, such as your mergefactor (if you have many files, the number of open files will be large as well - this is especially true for the indices that aren't full imports. Check the number of files in your data directories and issue an optimize if the same index has become very fragmented and have a large mergefactor), number of searchers, other software running on the same server, etc.
- It could. Yes (or at least it won't function properly, as it won't be able to open any new files). No. In practice you'll get a message about being unable to open a file with the message "Too many open files".
QUESTION
I tried to install memory pool plugin but it is pointing to incorrect location https://java.net/downloads/memorypoolview/com-kodewerk-visualvm-memorypoolsb4.nbm. How do I install memory pool plugin?
...ANSWER
Answered 2017-Sep-14 at 14:35As you can see from URL this plugin is not developed by VisualVM devs. It was a separate project at java.net. Unfortunately java.net was discontinued and the author of the memory pool plugin did not set up new project yet. There is already a discussion about the memory pool plugin at new visualvm home at github.
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