🚀 go-pugleaf

From: harvard!wjh12!panda!teddy!jpn (John P. Nelson)
Date: Mon, 9 Dec 85 11:35:09 est

>I decided to do a little testing to see how much the size of my
>environment affected response time.
>

I suspected that the iteration time was affected by the shell searching the
environment, rather than an increase in fork/exec time.  I wrote a C program
to do the same thing as the shell script written by John P. Linderman.  I
was wrong!

The following results were achieved on a diskless SUN-2 workstation (a
"perfmeter" running along side indicated 100% cpu usage, and 0% ethernet
activity - apparently everything remained in memory) I would have used a VAX,
but didn't want to annoy my fellow employees).  Your numbers will vary:

% testit
Env size 56, loop time 135
Env size 113, loop time 139
Env size 227, loop time 158
Env size 455, loop time 167
Env size 911, loop time 207
Env size 1823, loop time 292
Env size 3647, loop time 470
Env size 7295, loop time 846
fork or exec failure: terminating


John P. Nelson (decvax!genrad!teddy!jpn seismo!harvard!talcott!panda!teddy!jpn)

--- cut here.  testit.c follows: ---
#include <stdio.h>

char *env[2];
char *echoargv[] =
    {
    "echo",
    "abc",
    (char *) 0
    };

#define DEFAULTENV "TEST=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
#define INNERLOOP 1000

main()
    {
    extern char *malloc(), *realloc();
    register int i;
    register char *ptr;
    long starttime;
    long endtime;
    int waitst;

    env[0] = malloc(sizeof(DEFAULTENV));
    strcpy(env[0], DEFAULTENV);
    env[1] = 0;
    close(1);			/* close up stdout */
    if (open("/dev/null", 2) < 0)
	{
	fprintf(stderr, "Can't open /dev/null on 1\n");
	}

    while (1)	/* or until failure */
	{
	time(&starttime);
	for (i = 0; i < INNERLOOP; ++i)
	    {
	    /* do the fork/exec */
	    if (fork() == 0)
		{
		execve("/bin/echo", echoargv, env);
		exit(-1);		/* exec failure */
		}

	    /* terminate on anything but successfull exit(0) */
	    if (wait(&waitst) < 0 || (waitst & 0xFFFF) != 0)
		{
		fprintf(stderr, "fork or exec failure: terminating\n");
		exit(0);
		}
	    }
	time(&endtime);
	fprintf(stderr, "Env size %d, loop time %ld\n",
		strlen(env[0]), endtime - starttime);
	/* now double the environment size */
	env[0] = realloc(env[0], (strlen(env[0])+1) * 2);
	ptr = env[0] + strlen(env[0]);		/* point to trailing null */
	strcpy(ptr+1, env[0]);			/* tack on another copy */
	*ptr = '\n';				/* and join the two strings */
	}
    /* NOTREACHED */
    }

Volume-Number: Volume 4, Number 7