SOS S

1
???S????OS? ?????????????S
2
??sa????

• ??e??a st?? ????te?t????? ?p?????st??
• S?ed?as? epe?e??ast? ??a t?? e?t??es? 1 thread
  (pipeline, branch prediction)
• S?ed?as? ??a t?? e?t??es? n threads (SMT resource
  allocation, threads scheduling)
• ?te???e?e?? a???te?t?????? (Cell)
• ?a??????a s?st?µata
• ?e?a???a µ??µ?? (cache sharing, coherence
  protocols, NUMA architectures)
• ???t?a d?as??des?? (on-chip interconnection
  networks)
• Virtualization
• ?a?????? pa???????? ??d??a (synchronization
  costs, locks, Transactional Memory, automatic
  parallelization)

3
??sa????

• ???s? ?pa????t?? µ??a??µ?t??
• ?e???? ??st?? (p?. Sun SPARC Enterprise T5120
  server (64 threads, 128GB mem) 12.800 )
• ?d??aµ?a pa??µßas?? st? ????? t??? (s???e???µ???
  pipeline, caches, interconnection network)
• ?e?????sµ??? d??at?t?ta pa?a???????s?? ?a?
  µet??se?? (p.?. performance counters ?????,
  µ???? documentation)
• ?e?????sµ?? st? s?µe?a. ??? µe?et?? µe????t????
  a???te?t?????? (p.?. chip µe 100 ? 1000 threads)
• ??s? Simulation (p??s?µ???s?)

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???s?µ???s? ????te?t?????? (1)

• ??e??e?t?µata
• ??af??et??? ep?peda ?ept?µ??e?a? ?a? a???ße?a?
• Pipelines, caches, branch predictors,
• Hardware devices (timer, drives, cards, )
• ?????? d?af??e?a ?a? e?????a pa?a???????s?? ?a?
  µet??se??
• ??e???? ?a???t?µ?? p??t?se??/?de??
• ??st??
• Open source (Free)
• Academic licenses (Free ? µ???? ??st?? ??a
  support)

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???s?µ???s? ????te?t?????? (2)

• ??????se??
• ?????? a??pt???? t?? µ??t???? (modeling time)
• ??e???? ????t?ta? µ??t???? (validation)
• ?a??t?ta
• Active research field
• ??????a ep??????
• Virtutech Simics (x86, SPARC, MIPS, Leon, )
• AMD SimNow (x86)
• Simplescalar (Alpha)
• SMTSIM (Alpha SMT)

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??atf??µe? ???s?µ???s??

• ???f???? t?p?? p??s?µ???t??
• Trace-driven vs. Execution-driven
• Cycle-level accurate vs. Functional models
• Full system simulators (p.?. Simics)
• ???f???? t?p?? p??s?µ???s??
• ?????? e?t??es? efa?µ????
• ???s? stat?st???? µe??d??

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Functional vs. Timing Simulation

• Functional Simulation
• ???s?µ???s? t?? ?e?t???????t?ta? t?? e?t????
  (instructions semantics and functionality)
• ?etaß??? t?? state (registers, memory, )
• S?st? program output
• Timing Simulation
• Functional simulation
• ?ept?µe??? ???p???s? t?? d?af??et???? d?µ?? p??
  ???s?µ?p?????ta?
• ?????sµ?? ?e????t??, p???e?µ???? ?a ?p?????s?e? ?
  ?????? e?t??es?? t?? p?????µµat??
• Functional simulation p??? p?? ???????

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Full System Simulator

• ?????? d?aded?µ???? p??s?µ???t?? (p.?.
  Simplescalar) p??s?µ??????? µ??? t?? ??d??a t??
  efa?µ???? p?? ep????e? ? ???st??
• ???e??? OS
• Hack ??a t?? p??s?µ???s? system calls
• Full system simulators
• ?ea??st????
• ???s?µ???s? OS (p.?. Simics boots Linux)
• ????ße?a (accuracy)
• ?a??t?ta

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?a??de??µa ?????? p??s?µ???s??

• spec2k with gcc and small inputs

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?p????? pe??ß?????t?? p??s?µ???s??

• ???t???a ?p??????
• Modularity simulator
• Extensibility simulator
• ?p?ped? a???ße?a? simulator
• ?a??t?ta simulator
• ???e??? t?? design space p?? ?????µe ?a
  µe?et?s??µe
• ?p????? ?at??????? benchmarks

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Stat?st??? ???s?µ???s??

• ? s??p?? e??? timing simulation e??a? ?
  s?????t??s? p????f????? ?a? µ?t??s? d?af????
  µe?e???
• IPC
• Memory access cycles
• On-chip network contention
• ?a p?????µµata pa???s?????? d?af??et???? f?se??
• Initialization phase
• Main phase
• Wrap-up phase
• ??te pa?????µe ta stat?st??? p?? µa? e?d?af?????

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Stat?st??? ???s?µ???s??
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Simics

• Full system simulator
• ?p?st????? d?af??et???? s?st?µ?t?? (x86, Sun,
  ARM, )
• ??t??es? OS ?a? workloads ????? p??s???e?/a??a???
• ?????st? interface ??a microarchitecture modeling
• O Simics pa???e? t? functional simulation ?a? ?
  ???st?? ap?fas??e? ??a t? timing t?? d?af????
  ?e????t??
• ???p???se?? cache memories
• ??????st??s? ??a s?????t??s? p????f????? ?at? t?
  run time
• ?????? ap?de?t?? st? architecture research
  community
• Ta t?? ???s?µ?p???s??µe st?? as??se??
• Academic license for NTUA

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Simics Terminology

• Host machine
• ?? µ?????µa/OS st? ?p??? t???e? ? Simics
• Target machine
• ?? µ?????µa/OS t? ?p??? p??s?µ????e? ? Simics
• ?e? apa?te?ta? ? a???te?t????? ?a? t? OS t?? 2
  µ??a??µ?t?? ?a e??a? ta ?d?a
• Compile se d?af??et??? µ??a??µata!
• Steps vs. cycles vs. instructions

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Simics Environment

• Command line interface, pa??µ??? µe t? gdb
• Scripting
• ???at?t?ta scripting ?a? se Python
• ???pt??? µ??t???? (C, Python)
• Checkpointing
• ??af??et???? t??p?? p??s?µ???s??
• Fast, stalls, MAI
• Speed vs. accuracy

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Simics Major Components

• Functional
• Modules
• C, Python, DML
• Devices, components, boards, machines
• ??e???p?????ta? µe Simics ? Python scripts
• Timing
• Memory, caches, Simics MAI
• ? ???st?? ????e? t?? ?a??ste??se?? t?? ???e
  module

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Simics Demo