Tsuna analyzes how match time it takes to make a context switch. All analyzed chips are Multi-core Intel CPUs. OS / scheduler used – standard Linux Kernel.
Results: depends on what we call a context switch (theoretical / real world) and what we measure is: 1000 ns – 4500 ns (up to 45000 ns – depends on performance penalties involved).
However thing that I didn’t know is – context switch can be 3 times slower in virtual environment such as VMware ESX server or VMware Workstation.
VMware vmrun command is very powerful feature of VMware Workstation and ESX server to automate things in virtual machines.
Configuring automated script for Windows 2008 Server and Windows 2008 R2 was easy task. Everything went as expected. However the same script failed on Windows Vista and Windows 7 with the following two errors:
for vmrun ... copyFileFromHostToGuest ...:
Error: You do not have access rights to this file
for vmrun ... runProgramInGuest ...:
I searched extensively, but couldn’t find anything that helped to get rid of these errors. Then I started thinking about, what is the difference between Windows Workstation and Windows Server editions. The answer is – UAC – User Account Control is enabled by default on workstations for administrator account.
Still looking for solid fix, but currently I have disabled UAC on these virtual machines.
To disable UAC on Windows 7, go to Start – type UAC – press enter – set slider to Never notify – restart computer if needed.
To disable UAC on Windows Vista, go to Control Panel – type uac in the search box – uncheck “Use User Account Control (UAC) to help protect your computer” – click OK.