CPU - ESX Test

This test alerts administrators to issues with the overall CPU usage of the ESX host across processors.

Target of the test : An ESX server host

Agent deploying the test : An internal/remote agent

Outputs of the test : One set of results the ESX server host that is monitored

Configurable parameters for the test
  1. Test period - How often should the test be executed
  2. Host - The host for which the test is to be configured.
  3. port - The port at which the specified host listens. By default, this is NULL.
  4. esx user and esx password - In order to enable the test to extract the desired metrics from a target ESX server, you need to configure the test with an ESX USER and ESX PASSWORD. The user credentials to be passed here depend upon the mechanism used by the eG agent for collecting performance statistics from the ESX server and its VMs. These monitoring methodologies and their corresponding configuration requirements have been discussed hereunder:

    • Monitoring using the web services interface of the ESX server: Starting with ESX server 3.0, a VMware ESX server offers a web service interface using which the eG agent collects metrics from the ESX server. The VMware VI SDK is used by the agent to implement the web services interface. To use this interface for monitoring, this test should be configured with an ESX USER who has “Read-only” privileges to the target ESX server. By default, the root user is authorized to execute the test. However, it is preferable that you create a new user on the target ESX host and assign the “Read-only” role to him/her. The steps for achieving this have been elaborately discussed in Increasing the Memory Settings of the eG Agent that Monitors ESX Servers section.

      ESX servers terminate user sessions based on timeout periods. The default timeout period is 30 mins. When you stop an agent, sessions currently in use by the agent will remain open for this timeout period until ESX times out the session. If the agent is restarted within the timeout period, it will open a new set of sessions. If you want the eG agent to close already existing sessions before it opens new sessions, then you would have to configure all the tests with the credentials of an ESX user with permissions to View and stop sessions (prior to vSphere/ESX server 4.1, this was called the View and Terminate Sessions privilege). To know how to grant this permission to an ESX user, refer to Creating a Special Role on an ESX Server and Assigning the Role to a New User to the Server section.

      Sometimes, the VMware VI SDK may cache the hardware status metrics it collects and provide the test with the cached results. This may cause the eG agent to receive obsolete hardware status information from the SDK. This is also the reason why, you may at times notice a mismatch between the hardware status reported by the eG agent and by the vSphere client. To ensure that the eG agent always reports the current hardware status, you should configure the eG agent to obtain the hardware metrics from the VMware VI SDK only after the SDK resets the cache to clear its contents, and then refreshes the cache so that the latest hardware status information is fetched into it. To enable the eG agent to make the reset and refresh SDK calls, the esx user and esx password parameters must be configured with the credentials of a vSphere user with the Change Settings privilege. For that you need to create a special role on vSphere, assign the Change Settings privilege to that role, and then map the role with a new user on vSphere. The procedure for this is detailed in Configuring the eG Agent to Collect Current Hardware Status Metrics section.

    • Monitoring using the vCenter in the target environment: By default, the eG agent connects to each ESX server and collects metrics from it. While this approach scales well, it requires additional configuration for each server being monitored. For example, separate user accounts may need to be created on each server for read-only access to VM details. While monitoring large virtualized installations however, the agents can be optionally configured to monitor ESX servers using the statistics already available with different vCenter installations in the environment.

    In this case therefore, the ESX USER and ESX PASSWORD that you specify should be that of an Administrator or Virtual Machine Administrator in vCenter. However, if, owing to security constraints, you prefer not to use the credentials of such users, then, you can create a special role on vCenter with ‘Read-only’ privileges.

    Refer to Assigning the ‘Read-Only’ Role to a Local/Domain User to vCenter section to know how to create a user on vCenter.

    If the ESX server for which this test is being configured had been discovered via vCenter, then the eG manager automatically populates the esx user and esx password text boxes with the vCenter user credentials using which the ESX discovery was performed.

    Like ESX servers, vCenter servers too terminate user sessions based on timeout periods. The default timeout period is 30 mins. When you stop an agent, sessions currently in use by the agent will remain open for this timeout period until vCenter times out the session. If the agent is restarted within the timeout period, it will open a new set of sessions. If you want the eG agent to close already existing sessions before it opens new sessions, then you would have to configure all the tests with the credentials of a vCenter user with permissions to View and stop sessions (prior to vCenter 4.1, this was called the View and Terminate Sessions permission). To know how to grant this permission to a user to vCenter, refer to Creating a Special Role on vCenter and Assigning the Role to a Local/Domain User section. When the eG agent is started/restarted, it first attempts to connect to the vCenter server and terminate all existing sessions for the user whose credentials have been provided for the tests.

    This is done to ensure that unnecessary sessions do not remain established in the vCenter server for the session timeout period.  Ideally, you should create a separate user account with the required credentials and use this for the test configurations. If you provide the credentials for an existing user for the test configuration, when the eG agent starts/restarts, it will close all existing sessions for this user (including sessions you may have opened using the Virtual Infrastructure client). Hence, in this case, you may notice that your VI client sessions are terminated when the eG agent starts/restarts.

    Sometimes, the VMware VI SDK may cache the hardware status metrics it collects and provide the test with the cached results. This may cause the eG agent to receive obsolete hardware status information from the SDK. This is also the reason why, you may at times notice a mismatch between the hardware status reported by the eG agent and by the vSphere client. To ensure that the eG agent always reports the current hardware status, you should configure the eG agent to obtain the hardware metrics from the VMware VI SDK only after the SDK resets the cache to clear its contents, and then refreshes the cache so that the latest hardware status information is fetched into it. To enable the eG agent to make the reset and refresh SDK calls, the esx user and esx password parameters must be configured with the credentials of a vCenter user with the Change Settings privilege. For that you need to create a special role on vCenter, assign the Change Settings privilege to that role, and then map the role with a new user on vCenter. The procedure for this is detailed in Configuring the eG Agent to Collect Current Hardware Status Metrics section.

  5. confirm password - Confirm the password by retyping it here.
  6. ssl - By default, the ESX server is SSL-enabled. Accordingly, the SSL flag is set to Yes by default. This indicates that the eG agent will communicate with the ESX server via HTTPS by default.

    Like the ESX sever, the vCenter is also SSL-enabled by default. If you have chosen to use the vCenter for monitoring, then you have to set the SSL flag to Yes.

  7. webport - By default, in most virtualized environments, the vSphere/ESX server and vCenter listen on port 80 (if not SSL-enabled) or on port 443 (if SSL-enabled). This implies that while monitoring an SSL-enabled vSphere/ESX server directly, the eG agent, by default, connects to port 443 of the vSphere/ESX server to pull out metrics, and while monitoring a non-SSL-enabled server, the eG agent connects to port 80. Similarly, while monitoring a vSphere/ESX server via an SSL-enabled vCenter, the eG agent connects to port 443 of vCenter to pull out the metrics, and while monitoring via a non-SSL-enabled vCenter, the eG agent connects to port 80 of vCenter. 

    Accordingly, the webport parameter is set to 80 or 443 depending upon the status of the ssl flag.  In some environments however, the default ports 80 or 443 might not apply. In such a case, against the webport parameter, you can specify the exact port at which the vSphere/ESX server or vCenter in your environment listens so that the eG agent communicates with that port.

  8. VIRTUAL CENTER - If the eG manager had discovered the target ESX server by connecting to vCenter, then the IP address of the vCenter server used for discovering this ESX server would be automatically displayed against the vIRTUAL center parameter; similarly, the esx user and esx password text boxes will be automatically populated with the vCenter user credentials, using which ESX discovery was performed.

    If this ESX server has not been discovered using vCenter, but you still want to monitor the ESX server via vCenter, then select the IP address of the vCenter host that you wish to use for monitoring the ESX server from the vIRTUAL center list. By default, this list is populated with the IP address of all vCenter hosts that were added to the eG Enterprise system at the time of discovery. Upon selection, the esx user and esx password that were pre-configured for that vCenter server will be automatically displayed against the respective text boxes.

    On the other hand, if the IP address of the vCenter server of interest to you is not available in the list, then, you can add the details of the vCenter server on-the-fly, by selecting the Other option from the vIRTUAL center list. This will invoke the add vcenter server details page. Refer toAdding the Details of a vCenter Server for VM Discoverysection to know how to add a vCenter server using this page. Once the vCenter server is added, its IP address, esx user, and esx password will be displayed against the corresponding text boxes.

    On the other hand, if you want the eG agent to behave in the default manner -i.e., communicate with each ESX server for monitoring it - then set the VIRTUAL CENTER parameter to ‘none’. In this case, the ESX USER and ESX PASSWORD parameters can be configured with the credentials of a user who has at least ‘Read-only’ privileges to the target ESX server.

Measurements made by the test
Measurement Description Measurement Unit Interpretation

Overall physical CPU utilization:

Indicates the percentage of physical CPU used by the host.

Percent

A very high value for this measure indicates excessive CPU utilization by the host. The CPU utilization may be high because a few processes are consuming a lot of CPU, or because there are too many processes contending for a limited resource.

Overall physical CPU throttled:

Indicates the percentage of  scheduling limit over a past minute.

Percent

 

Overall physical CPU used:

Indicates the CPU usage in MHz of the VMware ESX host.

Mhz

 

Reserved capacity:

Indicates the total CPU capacity that is reserved by the VMs.

Mhz

 

Time in the COSTOP state:

Indicates the percentage of time the virtual host was ready to execute commands but was waiting for the availability of multiple pCPUs as the virtual host was configured to use multiple vCPUs.

Percent

If the virtual host is unresponsive and the value of this measure is high, it may indicate that the vSphere host has limited CPU resources to simultaneously co-schedule all pCPUs. If this value is low, then any performance problems should be attributed to other issues and not to the co-scheduling of the pCPU.

Total capacity

Indicates the total CPU capacity reserved by and available for virtual machines.

MHz

 

Demand

Indicates the total amount of CPU resources that all the powered on virtual machine on the host would use if there were no CPU contention or CPU limit.

MHz

By observing the variations to this measure over time, you will be able to judge how much CPU resources the VMs really require.

Latency

Indicates the percentage of time for which the powered on virtual machines on the host are ready to run, but are not running because they have reached their maximum CPU limit setting.

Percent

A high value of this measure is a cause for concern as it indicates that the VMs on the host have been non-operational for a long time for want of CPU resources. You may want to consider increasing the CPU limits, reservations, and shares for the VMs, so as to preempt such unpleasant situations.

Swap wait

Indicates the percentage of CPU time spent waiting for swap-in.

Percent

If the value of this measure is abnormally high, then check if the host has enough memory for running all VMs.

CPU wait

Indicates the percentage of CPU time spent in wait state.

Percent

CPU wait time includes CPU swap wait time, CPU idle time, and CPU I/O wait time.

If the value of this measure is abnormally high, then you may want to check the value of the CPU swap wait time and CPU idle time measures to know on what CPU was waiting the longest - was it waiting for swapping? was it waiting for an I/O operation to complete? or was it just being idle?

Ready

Indicates the total time that the virtual machines on the host were ready, but could not get scheduled to run on the physical CPU during last measurement interval.

Percent

This metric should typically be low - generally 5% or less. If VMs wait too long to run, it can significantly affect the responsiveness of the VMs.

CPU idle

Indicates the percentage of time that the CPU spent in an idle state.

Percent

If the CPU wait time measure is abnormally high, then compare the value of this measure with that of the Swap wait measure to know where the CPU spent maximum time - waiting for swapping? in the idle state? or waiting for an I/O operation?

vCPU vs pCPU utilization ratio

Indicates the ratio of the number of virtual CPUs utilized to the number of available physical CPUs.

Percent

pCPU or ‘physical’ CPU in its simplest terms refers to a physical CPU core i.e. a physical hardware execution context (HEC) if hyper-threading is unavailable or disabled. If hyperthreading has been enabled then a pCPU would consitute a logical CPU. This is because hyperthreading enables a single processor core to act like two processors i.e. logical processors. So for example, if an ESX 8-core server has hyper-threading enabled it would have 16 threads that appear as 16 logical processors and that would constitute 16 pCPUs.

As for a virtual CPU (vCPU) this refers to a virtual machine’s virtual processor and can be thought of in the same vein as the CPU in a traditional physical server. vCPUs run on pCPUs and by default, virtual machines are allocated one vCPU each. However, VMware have an add-on software module named Virtual SMP (symmetric multi-processing) that allows virtual machines to have access to more than one CPU and hence be allocated more than one vCPU.

The number of virtual machine vCPUs allocated compared to the number of physical CPU cores available is the vCPU-to-pCPU ratio. Determining this ratio will depend on the CPU utilization of the workloads.

If workloads are CPU-intensive, the vCPU-to-pCPU ratio will need to be smaller; if workloads are not CPU-intensive, the vCPU-to-pCPU ratio can be larger.

If the vCPU-to-pCPU ratio is too large - i.e., if the value of this measure is very high - it can result in high CPU Ready times. This may have a negative impact on the virtual machine's performance.

Here are some recommendations:

  • 1:1 to 3:1 - i.e., if the value of this measure varies between 100 % to 300% - it is no problem
  • 3:1 to 5:1- i.e., if the value of this measure is in the 300% - 500% range, it may begin to cause performance degradation
  • 6:1 or greater - i.e., any value that is 600% and over - is bound to cause a problem

Overall CPU core utilization

Indicates the CPU utilization of the corresponding core as a percentage during the interval.

Percent

This measure is reported only if hyper-threading is enabled.