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util.c
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util.c
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#include "util.h"
#include "mcslock.h"
#include <math.h>
#include <stdlib.h>
#include <sys/mman.h>
double d_gettimeofday()
{
int retval;
struct timeval tv;
retval = gettimeofday(&tv, NULL);
if (retval != 0) {
perror("gettimeofday");
exit(-1);
}
return (tv.tv_sec + ((double)tv.tv_usec) / 1000000.);
}
double avg(double *data, int samples)
{
int i;
double sum = 0;
for (i = 0; i < samples; i++) {
sum += data[i];
}
return sum / (double)samples;
}
double stdev(double *data, int samples)
{
int i;
double sumsq = 0;
double av;
for (i = 0; i < samples; i++) {
sumsq += data[i] * data[i];
}
av = avg(data, samples);
return sqrt(sumsq / samples - av * av);
}
double max(double *data, int samples)
{
int i;
double m = data[0];
for (i = 1; i < samples; i++) {
if (data[i] > m) {
m = data[i];
}
}
return m;
}
double min(double *data, int samples)
{
int i;
double m = data[0];
for (i = 1; i < samples; i++) {
if (data[i] < m) {
m = data[i];
}
}
return m;
}
/*
* In theory, we shouldn't need this, since with pthreads malloc() should
* suffice. However, malloc() proved finicky and addresses were getting
* corrupted. mmap() doesn't seem to suffer from this problem, so use
* it we shall.
*/
void *mapmem(size_t length)
{
return malloc(length);
// void *p;
// p = mmap(NULL, length,
// PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED,
// -1, (off_t)0);
// if (p == (void*)-1) {
// perror("mmap");
// exit(-1);
// }
// return p;
}
/* MCS locking operations. Put them here for the sake of convenience. */
void mcs_lock(mcslock *l, qnode_t *n)
{
qnode_t *pred;
/* Initialize my data. */
n->next = NULL;
n->locked = FALSE;
/* Enqueue myself. */
pred = (qnode_t*)atomic_xchg4((atomic_t*)l, (unsigned long)n);
if (pred != NULL) {
n->locked = TRUE;
pred->next = n;
}
/* Spin. */
while (n->locked) {
memory_barrier();
}
spin_lock_barrier();
}
void mcs_unlock(mcslock *l, qnode_t *n)
{
spin_unlock_barrier();
/* Fast exit if we're alone. */
if (n->next == NULL) {
if (CAS(l, n, NULL)) {
return;
}
}
/* Another processor executed a fetch-and-store (atomic_xchg4). Wait for
* it to set its locked and next fields. */
while (n->next == NULL) {
memory_barrier();
}
/* Signal the next waiting processor to go. */
n->next->locked = FALSE;
}