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Linux Monitoring

Web Stress Tool Linux Monitoring

Linux Monitoring Module

  • The Linux monitoring module allows NeoLoad to retrieve system information from Linux platforms during the test, connecting to your servers using either the Telnet or SSH protocol.
  • The Linux module has been validated on Fedora, Mandriva, Suse and Debian.
  • NeoLoad opens a session on the server, and uses system commands to retrieve the performance counters. The available counters are divided into 4 categories.

Linux Monitoring Features

Linux System Counters

  • CPU User :  Time spent running non-kernel code (user time, including nice time). Percentage of total CPU time.
  • CPU System :  Time spent running kernel code (system time). Percentage of total CPU time.
  • CPU Idle :  Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time. Percentage of total CPU time.
  • Interruptions Count :  Number of interrupts per second, including the clock.
  • Context Switch Count :  Number of context switches per second.
  • Processes Runnable :  Number of processes waiting for run time.
  • Processes Sleeping : Number of processes in uninterruptible sleep.
  • Processes Swapped : Number of processes swapped out but otherwise runnable. This field is calculated; however, Linux never desperation swaps.
  • Warning : This field is not accessible on all Linux operating systems (w field in the procs section of the vmstat command).

Linux Memory Counters

  • Total Memory : Total usable RAM (i.e. physical RAM minus a few reserved bits and the kernel binary code).
  • Memory Used : Total memory - Memory free.
  • Memory Free : The sum of LowFree+HighFree (overall stat).
  • Memory Buffered : Memory in buffer cache. Mostly useless as metric nowadays.
  • Memory Cache : Memory in the PageCache (DiskCache) minus SwapCache.
  • Total Swap : Total amount of physical swap memory.
  • Swap Free : Total amount of swap memory free.
  • Swap Used : Total Swap - Swap Free.

Linux Disk Counters (per device)

  • Disk Read Request Merged : The number of read requests merged per second issued to the device.
  • Disk Write Request Merged :  The number of write requests merged per second issued to the device.
  • Disk Read : The number of read requests issued to the device per second.
  • Disk Write : The number of write requests issued to the device per second.
  • Disk Read (sector) : The number of sectors read from the device per second.
  • Disk Write (sector) : The number of sectors written to the device per second.
  • Disk Read (KB) : The number of kilobytes read from the device per second.
  • Disk Write (KB) : The number of kilobytes written to the device per second.
  • Disk Request Size : The average size (in sectors) of the requests issued to the device.
  • Queue Length : The average queue length of the requests issued to the device.
  • IO Wait : The average time (in milliseconds) for I/O requests issued to the device to be served. This includes the time spent by requests in a queue and the time spent servicing them.
  • Disk Service Time : The average service time (in milliseconds) for I/O requests issued to the device.
  • IO CPU Time : Percentage of CPU time during which I/O requests are issued to the device (bandwidth utilization for the device). Device saturation occurs when this value is close to 100%.

Process Counters (per process)

  • Process Memory Usage : Resident size (kb). The non-swapped physical memory a task has used.
  • Process CPU Time : The task's share of the elapsed CPU time since the last update, expressed as a percentage of total CPU time.

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