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https://issues.apache.org/jira/browse/CLOUDSTACK-7857?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14213016#comment-14213016
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Anthony Xu commented on CLOUDSTACK-7857:
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_xs_memory_used is used as memory virtualization overhead in this XS host, but
the memory overhead varies a lot depending on the total host free memory, VM
density, VM memory size, VM guest OS type ...
to me, there seems no way to know the precise memory virtualization overhead
before you use the host to run VMs,
There are two ways CloudStack provides to mitigate this,
1. retry mechanism,
cloudstack uses retry in many places, like deployVM, startVM, migrateVM,
2. threshold,
cluster.memory.allocated.capacity.disablethreshold
you can use this per-cluster configuration to configure the free memory which
can be used by CloudStack.
If you have other thought on this, please share with us.
Anthony
> CitrixResourceBase wrongly calculates total memory on hosts with a lot of
> memory and large Dom0
> -----------------------------------------------------------------------------------------------
>
> Key: CLOUDSTACK-7857
> URL: https://issues.apache.org/jira/browse/CLOUDSTACK-7857
> Project: CloudStack
> Issue Type: Bug
> Security Level: Public(Anyone can view this level - this is the
> default.)
> Affects Versions: Future, 4.3.0, 4.4.0, 4.5.0, 4.3.1, 4.4.1, 4.6.0
> Reporter: Joris van Lieshout
> Priority: Blocker
>
> We have hosts with 256GB memory and 4GB dom0. During startup ACS calculates
> available memory using this formula:
> CitrixResourceBase.java
> protected void fillHostInfo
> ram = (long) ((ram - dom0Ram - _xs_memory_used) *
> _xs_virtualization_factor);
> In our situation:
> ram = 274841497600
> dom0Ram = 4269801472
> _xs_memory_used = 128 * 1024 * 1024L = 134217728
> _xs_virtualization_factor = 63.0/64.0 = 0,984375
> (274841497600 - 4269801472 - 134217728) * 0,984375 = 266211892800
> This is in fact not the actual amount of memory available for instances. The
> difference in our situation is a little less then 1GB. On this particular
> hypervisor Dom0+Xen uses about 9GB.
> As the comment above the definition of XsMemoryUsed allready stated it's time
> to review this logic.
> "//Hypervisor specific params with generic value, may need to be overridden
> for specific versions"
> The effect of this bug is that when you put a hypervisor in maintenance it
> might try to move instances (usually small instances (<1GB)) to a host that
> in fact does not have enought free memory.
> This exception is thrown:
> ERROR [c.c.h.HighAvailabilityManagerImpl] (HA-Worker-3:ctx-09aca6e9
> work-8981) Terminating HAWork[8981-Migration-4482-Running-Migrating]
> com.cloud.utils.exception.CloudRuntimeException: Unable to migrate due to
> Catch Exception com.cloud.utils.exception.CloudRuntimeException: Migration
> failed due to com.cloud.utils.exception.CloudRuntim
> eException: Unable to migrate VM(r-4482-VM) from
> host(6805d06c-4d5b-4438-a245-7915e93041d9) due to Task failed! Task record:
> uuid: 645b63c8-1426-b412-7b6a-13d61ee7ab2e
> nameLabel: Async.VM.pool_migrate
> nameDescription:
> allowedOperations: []
> currentOperations: {}
> created: Thu Nov 06 13:44:14 CET 2014
> finished: Thu Nov 06 13:44:14 CET 2014
> status: failure
> residentOn: com.xensource.xenapi.Host@b42882c6
> progress: 1.0
> type: <none/>
> result:
> errorInfo: [HOST_NOT_ENOUGH_FREE_MEMORY, 272629760, 263131136]
> otherConfig: {}
> subtaskOf: com.xensource.xenapi.Task@aaf13f6f
> subtasks: []
> at
> com.cloud.vm.VirtualMachineManagerImpl.migrate(VirtualMachineManagerImpl.java:1840)
> at
> com.cloud.vm.VirtualMachineManagerImpl.migrateAway(VirtualMachineManagerImpl.java:2214)
> at
> com.cloud.ha.HighAvailabilityManagerImpl.migrate(HighAvailabilityManagerImpl.java:610)
> at
> com.cloud.ha.HighAvailabilityManagerImpl$WorkerThread.runWithContext(HighAvailabilityManagerImpl.java:865)
> at
> com.cloud.ha.HighAvailabilityManagerImpl$WorkerThread.access$000(HighAvailabilityManagerImpl.java:822)
> at
> com.cloud.ha.HighAvailabilityManagerImpl$WorkerThread$1.run(HighAvailabilityManagerImpl.java:834)
> at
> org.apache.cloudstack.managed.context.impl.DefaultManagedContext$1.call(DefaultManagedContext.java:56)
> at
> org.apache.cloudstack.managed.context.impl.DefaultManagedContext.callWithContext(DefaultManagedContext.java:103)
> at
> org.apache.cloudstack.managed.context.impl.DefaultManagedContext.runWithContext(DefaultManagedContext.java:53)
> at
> com.cloud.ha.HighAvailabilityManagerImpl$WorkerThread.run(HighAvailabilityManagerImpl.java:831)
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