All Known Implementing Classes:

VmSchedulerAbstract, VmSchedulerSpaceShared, VmSchedulerTimeShared, VmSchedulerTimeSharedOverSubscription
```
public interface VmScheduler
```
An interface that represents the policy used by a Virtual Machine Monitor (VMM) to share processing power of a PM among VMs running in a host. Each host has to use is own instance of a VmScheduler that will so schedule the allocation of host's PEs for VMs running on it.
It also implements the Null Object Design Pattern in order to start avoiding NullPointerException when using the NULL object instead of attributing null to VmScheduler variables.

Since:

CloudSim Plus 1.0

Author:

Rodrigo N. Calheiros, Anton Beloglazov, Manoel Campos da Silva Filho

Field Summary

Fields
Modifier and Type Field Description

static VmScheduler NULL
An attribute that implements the Null Object Design Pattern for VmScheduler objects.

Method Summary

Modifier and Type	Method	Description
`boolean`	`allocatePesForVm(Vm vm)`	Requests the allocation of PEs for a VM, according to the number of PEs and MIPS defined by VM attributes.
`boolean`	`allocatePesForVm(Vm vm, java.util.List<java.lang.Double> requestedMips)`	Requests the allocation of PEs for a VM.
`void`	`deallocatePesForAllVms()`	Releases PEs allocated to all the VMs of the host the VmScheduler is associated to.
`void`	`deallocatePesFromVm(Vm vm)`	Releases all PEs allocated to a VM.
`void`	`deallocatePesFromVm(Vm vm, int pesToRemove)`	Releases a given number of PEs from a VM.
`java.util.List<java.lang.Double>`	`getAllocatedMips(Vm vm)`	Gets the MIPS share of each host's Pe that is allocated to a given VM.
`double`	`getAvailableMips()`	Gets the total amount of MIPS that is currently free.
`Host`	`getHost()`	Gets the host that the VmScheduler get the list of PEs to allocate to VMs.
`double`	`getMaxAvailableMips()`	Gets the maximum available MIPS among all the host's PEs.
`double`	`getMaxCpuUsagePercentDuringOutMigration()`	Gets the max percentage of CPU a VM migrating out of this Host can use.
`java.util.List<java.lang.Double>`	`getRequestedMips(Vm vm)`	Gets a copy of the List of MIPS requested by a VM, avoiding the original list to be changed.
`double`	`getTotalAllocatedMipsForVm(Vm vm)`	Gets the actual total allocated MIPS for a VM along all its allocated PEs.
`double`	`getVmMigrationCpuOverhead()`	Defines the percentage of Host's CPU usage increase when a VM is migrating in or out of the Host.
`boolean`	`isSuitableForVm(Vm vm)`	Checks if the PM using this scheduler has enough MIPS capacity to host a given VM.
`boolean`	`isSuitableForVm(Vm vm, java.util.List<java.lang.Double> requestedMips)`	Checks if a list of MIPS requested by a VM is allowed to be allocated or not.
`VmScheduler`	`setHost(Host host)`	Sets the host that the VmScheduler get the list of PEs to allocate to VMs.

- Field Detail
  - NULL
```
static final VmScheduler NULL
```
    An attribute that implements the Null Object Design Pattern for VmScheduler objects.
- Method Detail
  - allocatePesForVm
```
boolean allocatePesForVm(Vm vm,
                         java.util.List<java.lang.Double> requestedMips)
```
    Requests the allocation of PEs for a VM.
    
    Parameters:
    
    vm - the vm to allocate PEs to
    
    requestedMips - the list of MIPS share to be allocated to a VM
    
    Returns:
    
    true if the PEs were allocated to the VM, false otherwise
    
    To do something:
    
    All implementing classes don't consider the situation when a Vm already has allocated MIPS and the method is called again. In this case, what is supposed to do? Increase the current allocation or change it? I think that the obvious action is to change the allocation, however, the implementations aren't working to deal with this situation. For that, they have to use some method such as Resource.isAmountAvailable(long) to first check if the difference from the current allocated mips and the requested one is available. Currently the implementations wrongly check if the total requested mips is available, while only the difference has to be checked. It has to be added some tests to check this issue.
  - allocatePesForVm
```
boolean allocatePesForVm(Vm vm)
```
    Requests the allocation of PEs for a VM, according to the number of PEs and MIPS defined by VM attributes.
    
    Parameters:
    
    vm - the vm to allocate PEs to
    
    Returns:
    
    true if the PEs were allocated to the VM, false otherwise
  - deallocatePesForAllVms
```
void deallocatePesForAllVms()
```
    Releases PEs allocated to all the VMs of the host the VmScheduler is associated to. After that, all PEs will be available to be used on demand for requesting VMs.
  - deallocatePesFromVm
```
void deallocatePesFromVm(Vm vm)
```
    Releases all PEs allocated to a VM. After that, the PEs may be used on demand by other VMs.
    
    Parameters:
    
    vm - the vm to deallocate PEs from
  - deallocatePesFromVm
```
void deallocatePesFromVm(Vm vm,
                         int pesToRemove)
```
    Releases a given number of PEs from a VM. After that, the PEs may be used on demand by other VMs.
    
    Parameters:
    
    vm - the vm to deallocate PEs from
    
    pesToRemove - number of PEs to deallocate
  - getAllocatedMips
```
java.util.List<java.lang.Double> getAllocatedMips(Vm vm)
```
    Gets the MIPS share of each host's Pe that is allocated to a given VM.
    
    Parameters:
    
    vm - the vm to get the MIPS share
    
    Returns:
  - getAvailableMips
```
double getAvailableMips()
```
    Gets the total amount of MIPS that is currently free. If there are VMs migrating into the Host, their requested MIPS will already be allocated, reducing the total available MIPS.
    
    Returns:
  - getRequestedMips
```
java.util.List<java.lang.Double> getRequestedMips(Vm vm)
```
    Gets a copy of the List of MIPS requested by a VM, avoiding the original list to be changed.
    
    Parameters:
    
    vm - the VM to get the List of requested MIPS
    
    Returns:
  - isSuitableForVm
```
boolean isSuitableForVm(Vm vm)
```
    Checks if the PM using this scheduler has enough MIPS capacity to host a given VM.
    
    Parameters:
    
    vm - the vm to check if there is enough available resource on the PM to host it
    
    Returns:
    
    true, if it is possible to allocate the the VM into the host; false otherwise
    
    See Also:
    
    isSuitableForVm(Vm)
  - isSuitableForVm
```
boolean isSuitableForVm(Vm vm,
                        java.util.List<java.lang.Double> requestedMips)
```
    Checks if a list of MIPS requested by a VM is allowed to be allocated or not. Depending on the VmScheduler implementation, the return value of this method may have different effects:
    
    true: requested MIPS can be allocated, partial or totally;
    
    false: requested MIPS cannot be allocated because there is no availability at all or there is just a partial amount of the requested MIPS available and the VmScheduler implementation doesn't allow allocating less than the VM is requesting. If less than the required MIPS is allocated to a VM, it will cause performance degradation. Such situation defines an over-subscription situation which just specific VmSchedulers accept.
    Parameters:
    
    vm - the Vm to check if there are enough MIPS to allocate to
    
    requestedMips - a list of MIPS requested by a VM
    
    Returns:
    
    true if the requested MIPS List is allowed to be allocated to the VM, false otherwise
  - getMaxAvailableMips
```
double getMaxAvailableMips()
```
    Gets the maximum available MIPS among all the host's PEs.
    
    Returns:
  - getTotalAllocatedMipsForVm
```
double getTotalAllocatedMipsForVm(Vm vm)
```
    Gets the actual total allocated MIPS for a VM along all its allocated PEs. If the VM is migrating into the Host, then just a fraction of the requested MIPS is actually allocated, representing the overhead of the migration process.
    The MIPS requested by the VM are just actually allocated after the migration is completed.
    
    Parameters:
    
    vm - the VM to get the total allocated MIPS
    
    Returns:
    
    See Also:
    
    getVmMigrationCpuOverhead()
  - getMaxCpuUsagePercentDuringOutMigration
```
double getMaxCpuUsagePercentDuringOutMigration()
```
    Gets the max percentage of CPU a VM migrating out of this Host can use. Since there may be an overhead associated to the migration process (if the CPU overhead for VM migration is greater than 0), during the migration, the amount of MIPS the VM can use is reduced due to this overhead.
    
    Returns:
    
    the max percentage of CPU usage during migration (in scale from [0 to 1], where 1 is 100%)
  - getVmMigrationCpuOverhead
```
double getVmMigrationCpuOverhead()
```
    Defines the percentage of Host's CPU usage increase when a VM is migrating in or out of the Host. The value is in scale from 0 to 1 (where 1 is 100%).
    
    Returns:
    
    the Host's CPU migration overhead percentage.
  - getHost
```
Host getHost()
```
    Gets the host that the VmScheduler get the list of PEs to allocate to VMs.
    
    Returns:
  - setHost
```
VmScheduler setHost(Host host)
```
    Sets the host that the VmScheduler get the list of PEs to allocate to VMs. A host for the VmScheduler is set when the VmScheduler is set to a given host. Thus, the host is in charge to set itself to a VmScheduler.
    
    Parameters:
    
    host - the host to be set
    
    Returns:
    
    Throws:
    
    java.lang.IllegalArgumentException - when the scheduler already is assigned to another Host, since each Host must have its own scheduler
    
    java.lang.NullPointerException - when the host parameter is null

Interface VmScheduler

Field Summary

Method Summary

Field Detail

NULL

Method Detail

allocatePesForVm

allocatePesForVm

deallocatePesForAllVms

deallocatePesFromVm

deallocatePesFromVm

getAllocatedMips

getAvailableMips

getRequestedMips

isSuitableForVm

isSuitableForVm

getMaxAvailableMips

getTotalAllocatedMipsForVm

getMaxCpuUsagePercentDuringOutMigration

getVmMigrationCpuOverhead

getHost

setHost