Damn Simics
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Transcript of Damn Simics
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YANG DING @ CSE
What the hell isSimics?
September 21, 2007
(Part of the slides are from CSE 532 Tutorial)
NOTE: Some of the contents here are outdated.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.
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YANG DING @ CSE
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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YANG DING @ CSE
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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YANG DING @ CSE
Take a look
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YANG DING @ CSE
Another look
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YANG DING @ CSE
Last look
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YANG DING @ CSE
What to simulate?
Symmetric Multiprocessor
Glueless Multiprocessor
CPU
Uniprocessor
Multiple-CMP
CMP CMP
CMP CMP
P
Chip Multiprocessor (CMP)
P P P
$ $ $ $
Credit: GEMS@Wisc
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YANG DING @ CSE
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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YANG DING @ CSE
Full System Simulation• Microprocessor design• Memory studies• Device development• Operating system emulation• OS development• Debugging• High-availability testing
– Please see the “Simics:A Full System Simulation Platform” paper for the details.
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YANG DING @ CSE
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 parameter’s impact to the
performance.– Test out new synchronization
atoms/coherent protocol.
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YANG DING @ CSE
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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YANG DING @ CSE
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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YANG DING @ CSE
Simulator Translation Cache
• STC enables statistical-accuracy as well as efficiency.– a mechanism in the simulator to improve s
imulator performance. Among other things, it filters uninteresting memory accesses from the memory hierarchy.
– istc-disable– dstc-disable
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YANG DING @ CSE
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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YANG DING @ CSE
Start Simics• cd $SIMICS_HOME• ./simics• ./simics -x firststeps.simics• ./simics -c configuration• -stall• -no-win• -help
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YANG DING @ CSE
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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YANG DING @ CSE
Checkpoints
• Save the states:– simics> write-configuration blabla– simics> exit
• Resume– ./simics -c blabla– simics> read-configuration blabla
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YANG DING @ CSE
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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YANG DING @ CSE
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 instruction’s true dependencies are not completed.
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YANG DING @ CSE
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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YANG DING @ CSE
User Defined Timing Model
• Memory Hierarchy Interface– Instruction fetch visibility
• cpu0.instruction-fetch-mode instruction-cache-access-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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YANG DING @ CSE
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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YANG DING @ CSE
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-in
stall.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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YANG DING @ CSE
Setup Simics 2.2.12 (cont’d)
• 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 pr
ocessors
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YANG DING @ CSE
Setup Simics 3.0.11
• Simics 3.0.11 Base Install Directory: /home/software/simics-3.0.11– home/ contains configurations of the targe
t 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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YANG DING @ CSE
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 (shouldn’t 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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YANG DING @ CSE
Recompiling Simics (with user modules)
• Change dir to $SIMICS_HOME
• Edit compiler.mk– Change the CC variable in v9-sol8-64 and a
dd a CXX variable:CC=cc –Kpic
CXX=cc
• Type gmake
• You should have an executable called simics
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YANG DING @ CSE
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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YANG DING @ CSE
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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YANG DING @ CSE