LCA2004, one of best talks, 2004-01-17 4:25

Intention

• Simulation here and now technology
• E-Mail computer, good computer, probably simulated

Why simulation?

• niche technology:
  • slow, expensive, difficult
  • niche affair
  • VMware, 99% customers windows on windows
  • networks simpler
  • TCO less important
  • TCO == total cost ownership
• testing is more important
  • often not done or not done enough
• emerging properties
  • weird protocols that cut through firewalls
• hardware that is very capable
  • hardware offloads load from CPU, leaving CPU free
• simulation allows doing new different things
• software obsolescence is slowing
• hardware obsolescence is steady
• network obsolescence exists
• simulation can delay drop off
• use magic, simulation environment, to stretch out the lifetime of component

Linux for simulation

• open source simulators
  • QEMU, Bochs, Hercules (S390), …
• closed source simulators
  • VMware, Simics, …
  • Simics can stretch time frame, i.e. very fast computer
• network simulators
  • Simured, NS2, ,,
• Linux can simulate itself
  • Zxem
  • Vserve, not really
    • Vserve make chroot available
    • run away process will bring down everyones machine
  • UML - user-mode-linux
• practical simulation: uCLinux
  • palm pilot simulator
  • synthetic, accurate, 1 architecture, target speed, 2 pieces to email
  • multi CPU not supported
  • email hardware works
  • enable easier to reproduce faults by different people
• Bochs
  • doesn’t do PCI bus mastering
  • synthetic, not accurate, hotchpotch architecture, -100 times slower, 4 pieces to email
  • email: disk image 10Meg-64Meg-, BIOS, VGA BIOS, Simulator
• UML
  • not synthetic, accurate, hotchpotch architecture, 0.75x times target speed, 2 pieces to email
  • email: image, {kernel config,kernel}
  • kernel source code
  • port to IA64 pending????
  • good speed
  • latest patches 85% or better efficiency
  • software suspend now supported
  • Knopix will use swap by default without asking
• Hercules
  • one of the best open source free platform simulators that exists
  • synthetic, accurate, 3 architectures (at least) S370/S390/Z series, 90 times slower, 2 pieces to email
  • OS360
  • 64 bit laptop
  • test code on 64 bit architecture with z series emulation
  • Allan Cox Talk: “Space Invaders stole my Mouse”
  • email: disk image,
  • chapter removed from manual on Hercules by IBM
  • simulate 3 pin serial line for console
  • never trust a computer you can lift

Testing Exim

• email computer
• encapsulate nasty hacks, transport via E-Mail
• multiple Exims
• use single UML instance
  • multiple Exims
  • SMTP client/server testers
  • DNS with different zones
  • 40Meg image
• use nested UML and nested UML images
  • each computer has an image
  • outer UML with iptables
  • multiple inner UMLs
  • rate limit with iptables at top level
  • 100Meg compressed (estimated)

Demonstrations

• Hercules
  • OS/2 is used to display status screen for mainframes(?)
  • login: _root
  • password: root
  • test portability and reliability

Worked Examples

Challenge your thinking