What the hell is Simics

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What the hell isSimics?
NOTE Some of the contents here are outdated.
Esp. Simics 2.0 is no longer supported by
VirtuTech. You have to install and use Simics
3.0.

• September 21, 2007
• (Part of the slides are from CSE 532 Tutorial)

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Overview of Simics

• Virtutech Simics 3.0.x or 2.2.x
• Academic licenses available in department
• Get your own free for one year, renewable
• http//www.virtutech.com
• Full system simulator
• Operating System
• Libraries, Applications

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Some keywords

• Host Machine
• Where you run the simulation
• Windows, Linux, Solaris host machines
• Target Machine
• What you want to simulate
• Module
• Configuration
• Script

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Take a look
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Another look
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Last look
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What to simulate?
CPU
Uniprocessor
Credit GEMS_at_Wisc
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System level simulator

• Virtutech Simics is a full system simulation
  platform that provides a controlled,
  deterministic, and fully virtualized
  environment.
• Models the entire machine that OS sees
• it can run anything target system can
• Vital for tracing OS-intensive workload
• Simics is a hardware simulator

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Full System Simulation

• Microprocessor design
• Memory studies
• Device development
• Operating system emulation
• OS development
• Debugging
• High-availability testing
• Please see the SimicsA Full System Simulation
  Platform paper for the details.

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Simics helps a lot

• Used in various research areas
• Access to shared-memory system / message-passing
  system
• Run real parallel programs.
• Inspect what happens in the system. (e.g. examine
  cache coherent traffic.)
• Study the system parameters impact to the
  performance.
• Test out new synchronization atoms/coherent
  protocol.

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Fast or slow simulator?

• Simulate instruction by instruction
• Fast enough to run real applications
• 100x slowdown with statistics
• 5-10MIPS. Faster than sim-fast, a simulator in
  the simplescalar suite
• However, the truth is that simulation is always
  slow

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Flexibility with modules

• User pluggable modules enable detailed simulation
  of required hardware components
• Caches, out-of-order Microarchitecture,
• A variety of statistics available to use
• Simics API has more than 200 exported functions,
  several data types, and more than 50 predefined
  interfaces. The API is written in C.

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Simulator Translation Cache

• STC enables statistical-accuracy as well as
  efficiency.
• a mechanism in the simulator to improve simulator
  performance. Among other things, it filters
  uninteresting memory accesses from the memory
  hierarchy.
• istc-disable
• dstc-disable

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How to simulate multiprocessors?

• Simulate on each processor for certain number of
  cycles
• cpu-switch-time
• default 1000 cycles
• Cycles
• Number of cycles
• Steps
• Number of instructions (os and application)

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Start Simics

• cd SIMICS_HOME
• ./simics
• ./simics -x firststeps.simics
• ./simics -c configuration
• -stall
• -no-win
• -help

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Pause/Stop the simulation

• ctrl c
• Temporal breakpoint
• cc N (cycles)
• c N (steps)
• Memory/Register/IO breakpoint
• Graphics breakpoint
• Text output breakpoint
• magic breakpoint
• magic instruction

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Checkpoints

• Save the states
• simicsgt write-configuration blabla
• simicsgt exit
• Resume
• ./simics -c blabla
• simicsgt read-configuration blabla

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Access Host Files

• You can access the host file system by mounting
  it to the simulated machine.
• The /host file system is mounted as read-only
• Do not execute files on host system directly,
  instead, copy it to simulated machine and run

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Execution Model

• In-Order execution An instruction can not be
  issued unless the previous instruction completes,
  no matter how many simulated cycle it takes.
• Out-of-Order execution (only available for sparc
  targets). Instruction stalls only if the
  instructions true dependencies are not completed.

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Default Timing Model

• Default timing model
• In-Order execution An instruction use exact one
  clock cycle.
• Out-of-Order execution Control or data
  dependency will cost one clock cycle.

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User Defined Timing Model

• Memory Hierarchy Interface
• Instruction fetch visibility
• cpu0.instruction-fetch-mode instruction-cache-acce
  ss-trace
• Timing model
• User define a timing model function which will be
  called when memory request occurs.
• The function should return the number of cycles
  to stall the instruction.
• If return nonzero, Simics will stall that number
  of cycles

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Setup your own Simics

• Simics 2.2.12
• Build on what Chun LIU left years ago
• Simics 3.0.11
• Build on the department installation
• Simics 3.0.29
• Download it yourself
• Windows on x86
• Linux on x86
• Solaris on SPARC
• Linux on AMD64

Note As Simics is evolving quite rapidly and
many bugs are fixed in later versions, users are
generally recommend to upgrade. Possible
compatibility issues are read in the RELEASENOTES.
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Setup Simics 2.2.12

• 1. go to any directory you want to install
  simics-2.2.12
• 2. run /home/csl/chliu/simics-2.2.12/scripts/user-
  install.sh /home/scalp/chliu/simics-2.2.12/
• 3. run /home/mdl/yding/image/chliu.sh instead of
  /home/csl/chliu/simics-2.0/simics_install
• 4. go to simics-2.2.12/v9-sol8-64/lib
• 5. make v9
• 6. go to simics-2.2.12/home/sarek

Successfully tested on eru as of 09/21/2007
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Setup Simics 2.2.12 (contd)

• You have a version to run!
• ./simics -c s1p
• s2p, s4p, s8p as well in the directory
• Configurations from 2 to 24 processors available
  in /home/mdl/yding/image/
• You may not be able to access, though
• Most research work has results up tp 16
  processors

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Setup Simics 3.0.11

• Simics 3.0.11 Base Install Directory
  /home/software/simics-3.0.11
• home/ contains configurations of the target
  machines.
• src/ contains the framework for developing new
  Simics modules (including the examples).
• host/ (such as v9-sol8-64/ or amd64-linux/)
  contains the object files and specific modules or
  libraries developed by the user.

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Setup Simics 3.0.11

• Create Personal Workspace
• setenv SIMICS_HOME ./simics-workspace
• /home/software/simics-3.0.11/bin/workspace-setup
  SIMICS_HOME
• Change dir to SIMICS_HOME
• compiler.mk compiler configuration
• config.mk general configuration (shouldnt have
  to edit)
• GNUmakefile The Makefile
• modules/ user-created module source code
• simics simics executable
• targets/ configuration for various targets
• v9-sol8-64/ host-specific object and library
  files

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Recompiling Simics (with user modules)

• Change dir to SIMICS_HOME
• Edit compiler.mk
• Change the CC variable in v9-sol8-64 and add a
  CXX variable
• CCcc Kpic
• CXXcc
• Type gmake
• You should have an executable called simics ?

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Variations

• GEMS
• Wisconsin
• http//www.cs.wisc.edu/gems/
• Version 1.3
• Flexus
• CMU
• http//www.ece.cmu.edu/simflex/flexus.html
• Version 2.1.1

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Resources

• Some intruduction papers online, such as Simics
  A Full System Simulation Platform, IEEE Computer,
  2002
• Simics User Guide
• Much thinner than you think
• Read it first
• Simics Forum
• http//www.simics.net
• Quite a few people in CSE department

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