How does the linux out of memory oom killer affect a. Since a memory balloon works with an agent vmmemctrl driver in linux we can determine. How to determine the size of memory allocated by vmware ballooning driver shipped with red hat enterprise linux 67. In the benchmark example i am discussing here, the memory usage counter rose to 98% allocation. The vmkernel regularly reclaims unused virtual machine memory by ballooning and swapping. So it is definitely possible to tell, the question is how. What is happening here is that the vmware balloon driver has consumed over 20gb of memory because this virtual machine is on a vm host that is over committed on memory. Memory ballooning is a memory management feature used in most virtualization platforms which allows a host system to artificially enlarge its pool of memory by taking advantage or reclaiming unused memory previously allocated to various virtual machines.
Connect to your esxi host using vma, the dcui or putty needs ssh service running and run esxtop. To check that your vms have loaded and are running the vmware memory balloon driver in the guest os, you can use esxtop. The balloon driver is likely to become active when the total amount of ram allocated for all of the vms that are managed by a hypervisor exceeds the amount of ram available to the hypervisor itself. For more information, see the vsphere resource management guide. Memory resource management in vmware esx server carl a. Memory balloon active and reserving 20017 mb of ram. Vmware tools is required to be uptodate for the memory balloon driver vmmemctl to operate properly. Ballooning is an activity that happens when the esxi host is running out of physical memory. When the esxi host has 6% or less free memory available it will use the balloon driver to reclaim idle memory from virtual machines. Unfortunately, the balloon driver is unaware of memory pages. Vmmemctl is the balloon driver which is responsible to perform one of the memory management techniques memory ballooning in esxesxi hosts. Understanding memory resource management in vmware esx server. In a virtual machine, an inflating vmware balloon driver vmmemctl can trigger the oom killer.
Vmware tools status can be found from the summary tab of the virtual machine or go to the host and click on virtual machines tab to see the status of. The balloon driver is installed within the guest vm as part of the vmware tools package. The driver uses a proprietary ballooning technique that provides predictable performance that closely matches the behavior of a native system under similar memory constraints. Balloon driver retains hold on memory causing virtual machine. Vmware hosted oracle linux vm crashes at vmmemctl invoked. The balloon driver will inflate and because it is inside the operating system it will start by getting memory from the free list. Connect to your esxi host using vma, the dcui or putty needs ssh service running and run esxtop switch to the memory page press m. One of the vms has 768mb of memory reserved, yet here are the stats for memory.
Nov 29, 2010 the vmware memory balloon driver has potential to reduce the ram accessible to the os in an unpredictable way as does other vmware memory reclamation techniques. This is the same process of disabling balloon driver for linux machines. Checking that a vm has the vmware balloon driver running with esxtop. The vmkernel instructs the balloon driver to inflate by a certain amount of ram. Expand nonplug and play drivers and check the properties of the vmware server memory controller. The balloon driver is installed with vmware tools and is critical to performance.
When memory is overcommitted the esxi server reclaims memory by instructing the balloon driver to inflate by allocating pinned physical pages inside the guest os. If y means balloon driver is enabled and running and n means balloon driver not running. Oct 31, 2014 vmware memory ballooning, microsoft hyperv dynamic memory, and the open source kvm balloon process are similar in concept. Red hat shipped balloon driver is used in the system. The result of removing the balloon driver really comes down to how much you are overcommitting the memory of your hosts. This is a known bug in vmware tools and also openvmtools. The guest os may page out to its virtual disk when memory is scarce.
Installing vmware tools updates the buslogic driver within the guest operating system to the vmware supplied driver. Vmware esx is a hypervisor designed to efficiently manage hardware resources including cpu, memory, storage, and network among multiple concurrent virtual machines. The hypervisor will detect what memory the balloon driver has reclaimed and will free it up on the host physical memory layer. The way to avoid ballooning is not to uninstall the balloon driver but to create a. The memory balloon driver vmmemctl collaborates with the server to reclaim pages that are considered least valuable by the guest operating system. Troubleshooting sles vm memory issues suse communities. This technique effectively increases or decreases memory pressure on the guest operating system, causing the guest to invoke its own native memory management algorithms. Vmware tools memory balloon driver powered by kayako help. The memory balloon driver will be installed in the virtual machine with the help of vmware tools.
Although it is always desirable to have more than sufficient resources than required, we have. Verify that vmware tools is installed on each virtual machine. This is achieved through a balloon driver which is installed on the guest operating system. The driver acts like a balloon that can be inflated to reclaim physical pages by reserving them in the guest and invalidating them in the monitor, freeing up the underlying machine pages so they can be allocated to other guests. Feb 23, 2012 when the esxi host has 6% or less free memory available it will use the balloon driver to reclaim idle memory from virtual machines. If you have vmware tools installed inside the vm then you can find this out with.
Switch to the memory page press m press f to add a field. The ballooning driver inside the guest os will always know how much memory has been handed back to the host. The system is running low on the memory, still there is no process or processes which are consuming the memory. Vmware memory ballooning, microsoft hyperv dynamic memory, and the open source kvm balloon process are similar in concept. Jul 17, 2012 for some time during most of the vmware courses that i teach, the question of whether the balloon memory driver should be disabled has been raised. Performance troubleshooting vmware vsphere memory virtual. By default, memory stats view will not show the balloon drive stats. Ballooning requires cooperation between guest and host. Checking that a vm has the vmware balloon driver running. How vmware esx and esxi memory ballooning impacts access. Vmware tools status can be found from the summary tab of the virtual machine or go to the host and click on virtual machines tab to see the. The host uses balloon drivers running on the vms to determine how much memory it can take back from an underutilizing vm. Ballooning mechanism the balloon driver named vmmemctl, that is typically installed with vmware tools, is used to respond to commands from vmkernel to reclaim memory from that particular guest os. Dec 26, 2012 when the esxi host runs low on memory it uses the balloon driver to determine what memory the virtual machines can give up to prevent the host from paging to disk.
By unpredicatable i mean that, from the virtual machine perspective, there is no way of knowing how much memory will be reclaimed, where this memory will be reclaimed from kernal or. Modern hardware is, in many cases, using the new native drivers. Unfortunately, the balloon driver is unaware of memory pages locked by other processes. It is a memory reclamation technique using a balloon driver installed via vmware tools. Vmware actually has a kb article that has this information. It includes kernel modules for enhancing the performance of virtual machines running linux or other vmware supported unix like guest operating systems. The balloon driver communicates the physical page number for each allocated page to esx server, which may then reclaim the corresponding machine page. The balloon driver used for memory reclam ation on esx is part of vmware tools. Ballooning is a process where the esxi host reclaims memory back from the virtual machine. The balloon driver includes no external interfaces to the guest os and uses a private channel to communicate with the hypervisor and ensures that the reserved memory is available.
Part of this package that is installed is the balloon driver or vmmemctl which can be observed inside the guest. None of my other vms on my other servers show any ballooning, and no other vm on this host is ballooning. I believe there is a memory leak in the hpsa driver. How to find out what amount of memory a vmware balloon. But there might be issue of outofmemory like followings. The following drivers are only needed if you are running arch linux on a hypervisor like vmware vsphere. For some time during most of the vmware courses that i teach, the question of whether the balloon memory driver should be disabled has been raised. This is vmware physical memory management driver which acts like a balloon that can be inflated to reclaim physical pages by reserving them in the guest and invalidating them in the monitor, freeing up the underlying machine pages so they can be allocated to other.
Vmware ballooning is a feature that leverages the balloon driver vmmemctl included in the vmware tools installed in the guest os to release memory, in order to give it back to the host in case of contention. Is there a command i can run to show the driver memory usage. However, older hardware may still depend on a vmklinux driver module. But there might be issue of outof memory like followings. Nov 15, 2018 the balloon driver is installed within the guest vm as part of the vmware tools package. Vmware ballooning is a feature that leverages the balloon driver vmmemctl included in the vmware tools installed in the guest os to release memory, in. How to determine the size of memory allocated by vmware. This is the same process of disabling balloon driver for linux. Memory hotplugging on vmware reliability and alternatives. Performance tuning best practices for esx server 3 vmware. Generally, this does not impact virtual machine performance. I have two identical servers hp dl380 g7 which i recently added a p411 controller and a disk chassis. The balloon driver requests ram from the guest os and the guest allocates memory pages to the balloon driver. Checking that a vm has the vmware balloon driver running with.
The vmware memory balloon driver has potential to reduce the ram accessible to the os in an unpredictable way as does other vmware memory reclamation techniques. A reservation will not stop the vmmemctl from inflating and deflating the memory of a reserved mem vm, its based on memory resource demands of the vm. Select the virtual machines resources memory limit unlimited box. Oct 18, 2017 ballooning is a process where the esxi host reclaims memory back from the virtual machine. Memory used by vmware balloon driver is not visible on os doc id 2270987. Memory balloon driver when vmware tools are installed on a virtual machine they provide device drivers into the host virtualization layer, from within the guest operating system. Once you commit more memory to virtual machines than you have physical ram available, and the esx memory sharing is not able to save you any more ram, the next step would be for the balloon driver to start expanding on some of your servers. How does the linux out of memory oom killer affect a vmware. For instance a vm with mb memory the balloon can inflate to 650mb. As described earlier, vmware installs a balloon driver inside the guest os and signals the driver to begin to inflate when it begins to encounter contention for machine memory, defined as the amount of free machine memory available for new guest machine allocation requests dropping below 6%. If the guest os doesnt have a ballooning driver, then the host cannot take memory from the guest. This is vmware physical memory management driver which acts like a balloon that can be inflated to reclaim physical pages by reserving them in the guest and invalidating them in the monitor, freeing up the underlying machine pages so they can be allocated to other guests. This paper describes the basic memory management concepts in esx, the configuration. Detect memory ballooning from within the affected vm server fault.
We announced to deprecate the vmklinux driver stack back in 2017. I thought that it was something that warranted a blog, so here it is. Suse linux enterprise server 12 situation for the above sles server versions, running as virtual machines on vmware vsphere, the memory hotplugging feature is not consistently and reliably adding additional memory on the fly. The balloon driver notifies the vmkernel that the pages no longer hold vm data and puts the physical pages that used to back these vm pages into its free list. What is the impact of the vmklinux driver stack deprecation. Decrease the size of the balloon allowing guest to use more memory. This technique reduces the total number of memory pages consumed, which allows hosts to support higher levels of memory overcommitment. Once you commit more memory to virtual machines than you have physical ram available, and the esx memory sharing is not able to save you any more ram, the next step would be for the balloon driver to start expanding on some.
This is vmware physical memory management driver for linux. The vmware driver has certain optimizations that guestsupplied drivers do not. Jun 05, 2015 the vmkernel instructs the balloon driver to inflate by a certain amount of ram. How to find out what amount of memory a vmware balloon driver. Customer installed and enabled memory ballooning driver vmmemctl in vmware guest which is running an oracle linux. Vmware, virtualbox, xen and other hypervisor systems try to utilize the hardware.
Using the vsphere client, connect to the vcenter server. Where the memory went is essentially invisible to the standard utilities because it has been allocated directly in the kernel instead of to a normal process. The demand of the virtual machine is too high for the host to handle. For more information about memory ballooning please check out the memory resource management document put out by vmware. The memory ballooning allow reassign memory from idle vm to other vm which need more memory. Shortly after installation the server crashed with a.
Ballooning will not work if tools is not installed. To force the balloon driver to release its hold on memory and prevent the guest operating system from using swap space, use one of these options. The balloon driver can inflate up to a maximum of 65%. In linux use ps a and it is the vmmemctl process that should be present. I have a vm that shows high memory balloon average usage. However, this setting can cause the balloon driver to retain its hold on memory. This is a kms enabled drm driver for the vmware svga2 virtual hardware. Kubernetes, swap and the vmware balloon driver frankdenneman. To add the field, press f 3 press j to add the mctl stats and press enter to switch back to the memory stat view. Press space to return to the main memory view page of esxtop. The vmkernel selects the virtual machines with the largest amounts of idle memory detected by the idle memory tax process and will ask the virtual machine to select idle memory pages. Vmware kb 1003586 as the zing java virtual machine zvm is using locked memory pages provided by the zing system tools zst and the balloon driver is ignoring them, wrong assumptions are made over.
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