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Annotation of Net2/tests/benchmarks/csw.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Context switching benchmark.
                      3:  *
                      4:  * Force system to context switch 2*nsigs
                      5:  * times by forking and exchanging signals.
                      6:  * To calculate system overhead for a context
                      7:  * switch, the signocsw program must be run
                      8:  * with nsigs.  Overhead is then estimated by
                      9:  *     t1 = time csw <n>
                     10:  *     t2 = time signocsw <n>
                     11:  *     overhead = t1 - 2 * t2;
                     12:  */
                     13: #include <signal.h>
                     14: 
                     15: int    sigsub();
                     16: int    otherpid;
                     17: int    nsigs;
                     18: 
                     19: main(argc, argv)
                     20:        char *argv[];
                     21: {
                     22:        int pid;
                     23: 
                     24:        if (argc < 2) {
                     25:                printf("usage: %s nsignals\n", argv[0]);
                     26:                exit(1);
                     27:        }
                     28:        nsigs = atoi(argv[1]);
                     29:        signal(SIGALRM, sigsub);
                     30:        otherpid = getpid();
                     31:        pid = fork();
                     32:        if (pid != 0) {
                     33:                otherpid = pid;
                     34:                kill(otherpid, SIGALRM);
                     35:        }
                     36:        for (;;)
                     37:                sigpause(0);
                     38: }
                     39: 
                     40: sigsub()
                     41: {
                     42:        static mustreset = 1;
                     43:        int (*osig)();
                     44: 
                     45:        if (mustreset) {
                     46:                osig = signal(SIGALRM, sigsub);
                     47:                if (osig == sigsub)
                     48:                        mustreset = 0;
                     49:        }
                     50:        kill(otherpid, SIGALRM);
                     51:        if (--nsigs <= 0)
                     52:                exit(0);
                     53: }

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