6.7

n
Determine whether the high ready time for the virtual machine resulted from its CPU usage time
reaching the CPU limit setting. If so, increase the CPU limit on the virtual machine.
n
Increase the CPU shares to give the virtual machine more opportunities to run. The total ready time
on the host might remain at the same level if the host system is constrained by CPU. If the host ready
time does not decrease, set the CPU reservations for high-priority virtual machines to guarantee that
they receive the required CPU cycles.
n
Increase the amount of memory allocated to the virtual machine. This action decreases disk and or
network activity for applications that cache. This might lower disk I/O and reduce the need for the host
to virtualize the hardware. Virtual machines with smaller resource allocations generally accumulate
more CPU ready time.
n
Reduce the number of virtual CPUs on a virtual machine to only the number required to execute the
workload. For example, a single-threaded application on a four-way virtual machine only benefits from
a single vCPU. But the hypervisor's maintenance of the three idle vCPUs takes CPU cycles that could
be used for other work.
n
If the host is not already in a DRS cluster, add it to one. If the host is in a DRS cluster, increase the
number of hosts and migrate one or more virtual machines onto the new host.
n
Upgrade the physical CPUs or cores on the host if necessary.
n
Use the newest version of hypervisor software, and enable CPU-saving features such as TCP
Segmentation Offload, large memory pages, and jumbo frames.
Solutions for Memory Performance Problems
Host machine memory is the hardware backing for guest virtual memory and guest physical memory.
Host machine memory must be at least slightly larger than the combined active memory of the virtual
machines on the host. A virtual machine's memory size must be slightly larger than the average guest
memory usage. Increasing the virtual machine memory size results in more overhead memory usage.
Problem
n
Memory usage is constantly high (94% or greater) or constantly low (24% or less).
n
Free memory consistently is 6% or less and swapping frequently occurs.
Cause
n
The host probably is lacking the memory required to meet the demand. The active memory size is the
same as the granted memory size, which results in memory resources that are not sufficient for the
workload. Granted memory is too much if the active memory is constantly low.
n
Host machine memory resources are not enough to meet the demand, which leads to memory
reclamation and degraded performance.
n
The active memory size is the same as the granted memory size, which results in memory resources
that are not sufficient for the workload.
vSphere Monitoring and Performance
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