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shm.c
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shm.c
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/shm.h>
#include <sys/sem.h>
#include <sys/ipc.h>
#include <sys/types.h>
#include <sys/time.h>
typedef union {
int val;
struct semid_ds *buf;
unsigned short *array ;
struct seminfo *__buf;
void *__pad ;
} semun;
void sem_init(int sem_id, int sem_num, int init_valve)
{
semun sem_union;
sem_union.val = init_valve;
if (semctl(sem_id, sem_num, SETVAL, sem_union))
{
perror("semctl");
exit(-1);
}
}
void sem_release(int sem_id, int sem_num)
{
struct sembuf sem_b;
sem_b.sem_num = sem_num;
sem_b.sem_op = 1;
sem_b.sem_flg = 0;
if (semop(sem_id, &sem_b, 1) == -1)
{
perror("sem_release");
exit(-1);
}
}
void sem_reserve(int sem_id, int sem_num)
{
struct sembuf sem_b;
sem_b.sem_num = sem_num;
sem_b.sem_op = -1;
sem_b.sem_flg = 0;
if (semop(sem_id, &sem_b, 1) == -1)
{
perror("sem_reserve");
exit(-1);
}
}
double getdetlatimeofday(struct timeval *begin, struct timeval *end)
{
return (end->tv_sec + end->tv_usec * 1.0 / 1000000) -
(begin->tv_sec + begin->tv_usec * 1.0 / 1000000);
}
int main(int argc, char const *argv[])
{
#define SHM_KEY 0x1234
#define SEM_KEY 0x5678
#define WRITE_SEM 0
#define READ_SEM 1
pid_t pid;
int sem_id;
int shm_id;
int count, i, size;
struct timeval begin, end;
if (argc != 3)
{
printf("usage: ./shm <size> <count>\n");
return 1;
}
size = atoi(argv[1]);
count = atoi(argv[2]);
unsigned char *buf = malloc(size);
pid = fork();
if (pid == -1)
{
perror("fork");
return -1;
}
else if (pid == 0) // parent
{
sem_id = semget(SEM_KEY, 2, 0600 | IPC_CREAT);
if (sem_id == -1)
{
perror("parent: semget");
return -1;
}
sem_init(sem_id, WRITE_SEM, 1);
sem_init(sem_id, READ_SEM, 0);
shm_id = shmget(SHM_KEY, size, IPC_CREAT | 0600);
if (shm_id == -1)
{
perror("parent: shmget");
return -1;
}
void *addr = shmat(shm_id, NULL, 0);
if (addr == (void *)-1)
{
perror("parent: shmat");
return -1;
}
for (i = 0; i < count; i++)
{
sem_reserve(sem_id, READ_SEM);
memcpy(buf, addr, size);
// printf(">>>>>>>>%d\n", *(int*)buf);
sem_release(sem_id, WRITE_SEM);
}
if (shmdt(addr) == -1)
{
perror("child: shmdt");
return -1;
}
}
else // child
{
sleep(1);
sem_id = semget(SEM_KEY, 0, 0);
if (sem_id == -1)
{
perror("child: semget");
return -1;
}
shm_id = shmget(SHM_KEY, 0, 0);
if (shm_id == -1)
{
perror("child: shmget");
return -1;
}
void *addr = (int *)shmat(shm_id, NULL, 0);
if (addr == (void *)-1)
{
perror("child: shmat");
return -1;
}
gettimeofday(&begin, NULL);
for (i = 0; i < count; i++)
{
sem_reserve(sem_id, WRITE_SEM);
// *(int*)buf = i;
memcpy(addr, buf, size);
sem_release(sem_id, READ_SEM);
}
gettimeofday(&end, NULL);
double tm = getdetlatimeofday(&begin, &end);
printf("%.0fMB/s %.0fmsg/s\n",
count * size * 1.0 / (tm * 1024 * 1024),
count * 1.0 / tm);
sem_reserve(sem_id, WRITE_SEM);
semun dummy = {0};
semctl(sem_id, 0, IPC_RMID, dummy);
if (shmdt(addr) == -1)
{
perror("shmdt");
return -1;
}
shmctl(shm_id, IPC_RMID, 0);
}
return 0;
}