Efficient software checkpointing framework for speculative techniques

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Efficient software checkpointing framework for
speculative techniques

• ECE Connections 2006
• Co-Supervisors Prof. Greg. Steffan
• Prof. Cristiana Amza
• Chuck (Chengyan) Zhao
• Department of Computer Science
• University of Toronto
• Jun. 09, 2006

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Chip Multi-Processor (CMP) is now everywhere

• IBM
• Power 4
• Power 5
• Intel
• Montecito
• Smithfield
• AMD
• dual-core Opteron, Athlon X2
• Four-core Opteron
• Sun
• UltraSparc T1 32 cores
• UltraSparc T2 64 cores
• Sony, Toshiba, IBM
• Cell9 cores

Power 4
Dual-core Intel chip
Cell
Dual-core Opteron
use CMP for single-threaded applications through
parallelization
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Parallelization Techniques

• Automatic Parallelization
• conservative precise prove of non dependence
• limited domain
• Speculative Parallelization
• non-conservative
• has to recover from failures

focus speculative parallelization, use TLS
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Thread-Level Speculation (TLS) Parallelism

• Code example

for ( ) p q

• difficult to parallelize automatically
• uncertain dependence between p and q
• might be runtime or user-input dependent

checkpointing scheme dependence testing
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How Thread-Level Speculation works
?
Exec. Time
exploit available thread-level parallelism
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Memory Checkpointing Compiler Transformations

• mark region of interest
• backup each memory write (store)
• generate buffer refresh calls
• generate recovery code
• remove region marking delimiters

start_instrument() setjmp(buf1) for()
refresh_ckpt() backup_mem(a) a
backup_mem(b) b if(error_spec())
ckp_restore()
longjmp(buf1) stop_instrument()
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Preliminary Results MCF in SPEC2KINT
index fname
1 refresh_potential()
2 bea_compute_red_cost()
3 primal_bea_mpp()
4 1 2
5 1 3
6 2 3
7 1 2 3
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Challenges and Future Work

• Challenges software overhead
• Proposed Solutions optimizations
• inlining
• optimal buffer sizing and refreshing placement
• memory optimizations
• Applications
• value prediction
• debugging support
• reliability enhancement
• TLS (long term)
• ...

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Questions and Answers