source: benchmark/basic/ttst_lock.c @ 2316525

arm-ehenumforall-pointer-decayjacob/cs343-translationjenkins-sandboxnew-astnew-ast-unique-exprpthread-emulation
Last change on this file since 2316525 was 525b5ef, checked in by Peter A. Buhr <pabuhr@…>, 3 years ago

add documentation

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