But unfortunately most specialists insist on disabling the mechanism. Why is disabling the ballooning mechanism bad? Many organizations that deploy virtual infrastructures rely on memory overcommitment to reach a higher consolidation ratio and higher memory utilization. In a virtual infrastructure not every virtual machine is actively using its assigned memory at the same time and not every virtual machine is making use of its configured memory footprint.
To allow memory overcommitment, the VMkernel uses different virtual machine memory reclamation mechanisms. Transparent Page Sharing 2. Ballooning 3.
Memory compression 4. Host swapping Except from Transparent Page Sharing, all memory reclamation techniques only become active when the ESX host experiences memory contention. The VMkernel will use a specific memory reclamation technique depending on the level of the host free memory.
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. When the Guest OS stops using the page internally, it will remove the page from the allocated memory list and place it on the free memory list. Because no data is changed, ESX will keep storing this data in physical memory.
When the Balloon driver is utilized, the balloon driver request the guest OS to allocated a certain amount of pages.
If the virtual machine has enough idle pages no guest-level paging or even worse kernel level paging is necessary. Scott Drummonds tested an Oracle database VM against an OLTP load generation tool and researched the lack of impact of the balloon driver on the performance of the virtual machine. The results are displayed in this image: Impact on performance: Ballooning versus swapping.
Results of two experiments are shown on this graph: in one memory is reclaimed only through ballooning and in the other memory is reclaimed only through host swapping.
If the ESX server must begin to swap out guest memory, the choice of mem pages swapped out may be less than optimum for a guest's performance. Thanks a lot, johnwvmw for the comments in comment Resolving this issue as fixed. Skip to content. Star 1. New issue. Jump to bottom.
Copy link. Please help. The balloon driver is not associated with open-vm-tools. Ballooning is a process where the ESXi host reclaims memory back from the virtual machine. Ballooning is an activity that happens when the ESXi host is running out of physical memory. The demand of the virtual machine is too high for the host to handle. Each VM has a driver installed via VMware tools.
This driver is called a Balloon Driver. The guest operating system is able to decide which memory pages should be swapped to disk. When the host needs to free up some memory it will notify a special driver vmmemctl that is installed as part of the VMTools. This driver then consumes some of the memory that the guest OS believes is physically present in the virtual machine.
The guest OS will then swap memory to disk reducing the load on the. The guest OS will then swap memory to disk reducing the load on the host's physical memory. The host will then reallocate that memory to other virtual machines. By inflating the balloon, a virtual machine consumes less physical memory on the host, but more physical memory inside the guest. As a result, the hypervisor offloads some of its memory overload to the guest operating system while slightly loading the virtual machine.
That is, the hypervisor transfers the memory pressure from the host to the virtual machine. Ballooning induces guest memory pressure. In response, the balloon driver allocates and pins guest physical memory.
If the virtual machine has plenty of free guest physical memory, inflating the balloon will induce no paging and will not impact guest performance. You might ask what if and how to disable the VMware balloon driver within the guest OS. Is it a good idea? Well, there is a VMware KB article which talks about the Disabling the balloon driver rather outdated. IMHO I don't see much interest in doing that.
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