ADTarm-ehast-experimentalenumforall-pointer-decayjacob/cs343-translationnew-astnew-ast-unique-exprpthread-emulationqualifiedEnum
Last change
on this file since cadec25 was
525b5ef,
checked in by Peter A. Buhr <pabuhr@…>, 5 years ago
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add documentation
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Property mode set to
100644
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File size:
1.5 KB
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1 | #include <stdio.h> |
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2 | #include <stdint.h> // uintptr_t |
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3 | |
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4 | #include "bench.h" |
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5 | |
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6 | // Does a "lock xchg" on entry but a simple "mov" on exit => cheaper as 0 contention. While it has much more code, the |
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7 | // bulk is never run. |
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8 | |
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9 | #define CALIGN __attribute__(( aligned (CACHE_ALIGN) )) |
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10 | #define CACHE_ALIGN 128 |
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11 | #define Pause() __asm__ __volatile__ ( "pause" : : : ) |
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12 | |
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13 | typedef uintptr_t TYPE; // addressable word-size |
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14 | static volatile TYPE lock __attribute__(( aligned (128) )); // Intel recommendation |
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15 | static TYPE PAD CALIGN __attribute__(( unused )); // protect further false sharing |
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16 | |
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17 | static inline void spin_lock( volatile TYPE *lock ) { |
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18 | enum { SPIN_START = 4, SPIN_END = 64 * 1024, }; |
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19 | unsigned int spin = SPIN_START; |
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20 | |
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21 | for ( unsigned int i = 1;; i += 1 ) { |
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22 | if ( *lock == 0 && __atomic_test_and_set( lock, __ATOMIC_ACQUIRE ) == 0 ) break; |
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23 | for ( volatile unsigned int s = 0; s < spin; s += 1 ) Pause(); // exponential spin |
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24 | //spin += spin; // powers of 2 |
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25 | if ( i % 64 == 0 ) spin += spin; // slowly increase by powers of 2 |
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26 | if ( spin > SPIN_END ) spin = SPIN_START; // prevent overflow |
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27 | } // for |
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28 | } // spin_lock |
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29 | |
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30 | static inline void spin_unlock( volatile TYPE *lock ) { |
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31 | __atomic_clear( lock, __ATOMIC_RELEASE ); |
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32 | } // spin_unlock |
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33 | |
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34 | void __attribute__((noinline)) do_call() { |
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35 | spin_lock( &lock ); |
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36 | // asm volatile (""); |
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37 | spin_unlock( &lock ); |
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38 | } |
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39 | |
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40 | int main( int argc, char * argv[] ) { |
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41 | BENCH_START() |
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42 | BENCH( |
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43 | for (size_t i = 0; i < times; i++) { |
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44 | do_call(); |
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45 | }, |
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46 | result |
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47 | ) |
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48 | printf( "%g\n", result ); |
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49 | } |
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50 | |
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51 | // Local Variables: // |
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52 | // tab-width: 4 // |
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53 | // End: // |
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