Transcript Presentation

DTHREADS: Efficient Deterministic
Multithreading
Insanity: Doing the same
thing over and over again
and expecting different
results.
Tongping Liu, Charlie Curtsinger, Emery Berger
In the Beginning…
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There was the Core.
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And it was Good.
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It gave us our Daily Speed.
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Until the Apocalypse.
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And the Speed was no Moore.
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And then came a False Prophet…
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9
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Want speed?
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I BRING YOU THE GIFT OF PARALLELISM!
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color = ; row = 0; // globals
void nextStripe(){
for (c = 0; c < Width; c++)
drawBox (c,row,color);
color = (color == )?  : ;
row++;
}
for (n = 0; n < 9; n++)
pthread_create(t[n], nextStripe);
for (n = 0; n < 9; n++)
pthread_join(t[n]);
JUST USE THREADS…
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race conditions
pthreads
atomicity violations
deadlock
order violations
Salvation?
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race conditions
pthreads
D
THREADS
atomicity violations
deadlock
order violations
deterministic
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DTHREADS Enables…
Race-free Executions
Replay Debugging w/o Logging
Replicated State
Machines
runtime relative to pthreads
DTHREADS: Efficient Determinism
8.4
7.8
6
5
4
3
2
1
0
CoreDet
dthreads
pthreads
Usually faster than the state of the art
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runtime relative to pthreads
DTHREADS: Efficient Determinism
8.4
7.8
6
5
4
3
2
1
0
CoreDet
dthreads
pthreads
Generally as fast or faster than pthreads
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DTHREADS: Easy to Use
% g++ myprog.cpp –lpthread
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Isolation
shared address space
disjoint address spaces
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Performance: Processes vs. Threads
1.4
threads
processes
Normalized Execution Time
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1
2
1024
4
8
16
32
64
128
Thread Execution Time (ms)
256
512
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Performance: Processes vs. Threads
1.4
threads
processes
Normalized Execution Time
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1
2
1024
4
8
16
32
64
128
Thread Execution Time (ms)
256
512
29
Performance: Processes vs. Threads
1.4
threads
processes
Normalized Execution Time
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1
2
1024
4
8
16
32
64
128
Thread Execution Time (ms)
256
512
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“Shared Memory”
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“Shared Memory”
Snapshot pages
before modifications
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“Shared Memory”
Write back diffs
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Update in Deterministic Time & Order
Parallel
Serial
mutex_lock
“Thread” 1
cond_wait
“Thread” 2
pthread_create
“Thread” 3
Para
runtime relative to pthreads
DTHREADS performance analysis
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3
2
1
0
dthreads
pthreads
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The Culprit: False Sharing
Core 2
Core 1
Thread 1
Thread 2
Invalidate
Main Memory
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The Culprit: False Sharing
Core 2
Core 1
Thread 1
Thread 2
Invalidate
20x
Main Memory
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DTHREADS: Eliminates False Sharing!
Core 1
Process 1
Process 1
Process 2
Global State
Core 2
Process 2
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runtime relative to pthreads
DTHREADS: Detailed Analysis
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5
4
3
2
1
0
ordering only
isolation only
dthreads
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runtime relative to pthreads
DTHREADS: Detailed Analysis
6
5
4
3
2
1
0
ordering only
isolation only
dthreads
40
runtime relative to pthreads
DTHREADS: Detailed Analysis
6
5
4
3
2
1
0
ordering only
isolation only
dthreads
DTHREADS: Scalable Determinism
speedup of 8 cores over 2 cores
4
3
2
1
0
CoreDet
dthreads
pthreads
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DTHREADS: Scalable Determinism
speedup of 8 cores over 2 cores
4
3
2
1
0
CoreDet
dthreads
pthreads
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DTHREADS: Scalable Determinism
speedup of 8 cores over 2 cores
4
3
2
1
0
CoreDet
dthreads
pthreads
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DTHREADS
% g++ myprog.cpp –l pthread
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