I am using VirtualBox 5.1 running in a host with 48 CPU's and 250GB of RAM
the virtual machine that I am importing (the guest) initially had 2 CPU's and 4GB of RAM.
Inside this machine I am running a process with Java that starts a dynamic number of threads to perform some tasks.
I ran it with configurations below:
The whole process in my laptop (2 CPUs/4GB RAM) ~ 11 seconds
same program in the virtual machine in the server
(15 CPUs and 32GB of RAM) ~ 45 seconds
same program in the virtual machine in the server
(20 CPUs and 32GB of RAM) ~ 100+ seconds
same program in the virtual machine in the server
(10 CPUs and 32GB of RAM) ~ 5+ seconds
First I thought that there was a problem in how I was managing the threads from Java but after many tests I figured out that there was a relation between the number of CPU's that the virtual machine has and its performance, the maximum was 10, after that the overall performance of the machine slows down(CPU starvation?)
The virtual machine runs Oracle Enterprise Linux 6.7 and the host runs Oracle Enterprise Linux 6.9
I couldn't found any hard limit in the Virtual Machine documentation regarding the number of CPU's.
Is there a setting that needs to be set to enable/take advantage of more than 10 CPU's in a VirtualBox instance?
Time has happened since I posted this question, just for the archive I
will share my findings hoping they can help to save time for others.
It turns out that the performance issues were due to the way how VirtualBox works. Especially the relationship between the OS and the hypervisor.
The Virtual Machine (the guest OS) at the end is a single process for the host and when you modify the number of CPU's in the Virtual Machine settings what they will do is change the number of threads that the process will have to emulate the other CPU's. (at least in VirtualBox)
Having said that, when I assigned 10+ CPUs to the VM I ended up with:
a single process with 10+ threads
an emulated OS running hundreds of processes
my Java code which was creating another bunch of threads
All of that together caused that the setup was saturating the host Virtual Machine process which I think it was due to the way how the host OS was handling the processes context switching
On my server, the hard limit was 7 virtual CPU's, if I added more than that it would slow down the performance of the Java software
Running the Java software outside of the VM didn't show any performance issue, it worked out of the box with 60+ isolated threads.
We have almost the same setup as yours (Virtualbox running on a 48-core machine across 2 NUMA nodes).
I initially set the number of cores to the maximum supported in Virtualbox (e.g. 32), but quickly realized that one of the two NUMA nodes was always idling while the other stayed at medium loads, when the VM was under load.
Long story short, a process can only be assigned to a single NUMA node, and Virtualbox runs one user process with several threads... which means that we are limited to using 24 cores (and even less in practice considering that this is a 12-core cpu with hyperthreading).
Related
I understand that node.js can run on multiple cores on at least one CPU. What's not clear to me is whether it can run on more than one CPU. For example, if I have a 4-CPU machine with 10 cores in each CPU, can a single node.js process take advantage of all 40 cores, or just 10? Does it depend on the OS?
Other than performance effects (such as NUMA), multi-socket systems work exactly like single-socket-multi-core systems, whatever that implies for node.js. They're all SMP systems with multiple CPU cores and cache-coherent shared memory.
OSes will run threads across all physical cores in the system, so all that matters is that your workload is threaded at all.
The only thing that would be different is a cluster of machines with shared memory that's not cache-coherent; in that case you wouldn't be running a single instance of an OS across all the cores.
VMware ESXi 6.5 and later (VM version 13)
2x CPU (Xeon E5-2620 v3)
16,384 MB memory
Guest OS: Windows 10 Pro 1809 (build 17763.55)
Performance of the VM is very sluggish, even through the VMware console connection. Looking at the Resource Monitor, the tomcat9.exe process is the main hog of CPU time. This process has between 150-180 threads running and average CPU utilisation of around 75% with overall CPU hovering around 90-100%.
I have been reading that Tomcat should be able to run on minimal resources so there must be something else going on here. Unfortunately I know very little about Tomcat so am at a loss of what to look for. I have rebooted the VM and have nothing running on it (apart from the Resource Monitor).
Surely Tomcat should not be monopolising the CPU like this?
It also seems like a Java process is high on the CPU utilisation list. Conversely, we have another instance using Tomcat 8 on Windows 7 which is not taxing the CPU at all.
In this specific case, increasing the amount of memory available to the Java Virtual Machine (JVM) solved the problem.
Refer this article for How to Increase Java Memory in Windows
Simple question: Is it dangerous to activate KSM on a running hypervisor (Debian 8 with 3.16 kernel)?
Or is it recommended to shut down all virtual machines (KVM/qemu) first, then activate KSM and then start the virtual machines again?
We expect a memory saving of approx. 50% (we have a similar system where KSM is already active and there we effectively save almost 50% due to the always very similar VM appliances).
I have setup my development environment inside Virtual Machine running Ubuntu 14.04. My company doesn't allow me to run direct Linux Flavoured OS may be due to security reasons.
One thing I have observed is that in VM it only runs one task ast a time whereas if i run on my personal laptop it runs multiple tasks at a time.
Is there any way to configure poky in local.conf file for example or any other file for it to run multiple tasks at the same time. I have given more than 6 GB of RAM to the VM.
As it is running one task, build is taking a lot of time..
Thanks for your time
bitbake task executor enquires for number of CPUs dynamically, so it seems that you might have allocated 1 cpu to your VM. You might be able to see CPUs with below command in VM
lscpu
You might want to allocate more CPUs. VirtualBox lets you do that
Stop virtual machine
Click settings-> click system -> click processor -> Change the number of procesors.
i am trying to measure code performance (basically speed-up when using threads). So far i was using cygwin via windows or linux on separate machine. Now i have the ability to set up a new system and i am not sure whether i should have dual boot (windows and ubuntu) or a virtual machine.
My concern is whether i can measure reliable speed up and possibly other stuff (performance monitors) via a linux virtual machine or if i have to go with with normal booting in linux.
anybody have an opinion?
If your "threading" relies heavily on scheduling, I won't recommend you to use VM. VM is just a normal process from the host OS's point of view, so the guest kernel and its scheduler will be affected by scheduling by the host kernel.
If your "threading" is more like parallel computation, I think it's OK to use VM.
For me, it is much safer to boot directly on the system and avoid using a VM in your case. Even when you don't use a VM, it is already hard to have twice the same results in multi-threading because the system being used for OS tasks, so having 2 OS running in the same time as for VM even increases the uncertainty on the results. For instance, running your tests 1000 times on a VM would lead to, let's say, 100 over-estimated time, while it would maybe be only 60 on a lonely OS. It is your call to know if this uncertainty is acceptable or not.