Linux and Simulation
Speaker | Dad Shearer |
---|---|
Time | 2004-01-17 16:25 |
Conference | LCA2004 |
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