VMware posted on its website a paper titled: Interpreting esxtop 4.1 Statistics. esxtop is an utility provided by VMware which can be used to perform monitoring and collection of data for CPU, memory, disk and network. This document provides in depth and extensive information on how the statistics of esxtop can be interpreted and used.
The output of esxtop can be viewed in different types of screens one each for CPU statistics, memory statistics, network statistics, disk adapter statistics, disk device statistics, disk VM statistics and interrupt statistics. esxtop also provides a batch mode, where data can be redirected to a file for offline uses, or to use by other utilities.
The paper covers the following topics:
- Worlds and Groups, PCPUs and Statistics on Global and World
- Machine Memory and Guest Physical Memory
- Global and Group Statistics
- Adapter, Device, VM Screens
- Statistics on Disk, I/O throughput, Latency, Queue, Error, PAE, Split, Clone, ATS, Zero, Reservation
- Batch Mode Output
- Port and Port Statistics
- Batch Mode
"…It is important to note that some statistics refer to guest physical memory while others refer to machine memory. "Guest physical memory" is the virtual hardware physical memory presented to the VM. "Machine memory" is actual physical RAM in the ESX host. Let’s use the following figure to explain. In the figure, two VMs are running on an ESX host, where each block represents 4 KB of memory and each color represents a different set of data on a block.
Inside each VM, the guest OS maps the virtual memory to its physical memory. ESX Kernel maps the guest physical memory to machine memory. Due to ESX Page Sharing technology, guest physical pages with the same content can be mapped to the same machine page…"