ulimit on Sys V (was: BLAST experience sought)

[Theodore Hope]

In article <12796 at amdcad.UUCP> phil at amdcad.UUCP (Phil Ngai) writes:
>The 3B2 (awful) has a default file limit size of around 1 megabyte.
>Only the superuser can raise this limit with the "ulimit" command in
>sh.  (There is also a system call to change this.) The file transfer
>problem may not be in BLAST at all.

The 1-Meg ulimit problem can be fixed by changing the ulimit of the init
process to something more reasonable.  Since all processes inherit init's
ulimit, that would solve the problem.

crom at cuuxb posted the following program a few months ago.  It changes 
init's ulimit to the desired value.  On my 3b2/400 I placed it in the
/etc/brc initialization script.


--------cut here--------
/* setulimit: Written by crom at cuuxb (Michael C. Crom) 
 *
 *  This program finds init's ublock, and pokes a new ulimit into it.
 *
 */

#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/signal.h>
#include <sys/param.h>
#include <sys/dir.h>
#include <sys/proc.h>
#include <sys/user.h>
#include <sys/sbd.h>
#include <sys/var.h>
#include <nlist.h>

struct nlist nl[3] = {
	{ "v" },
	{ "proc" },
	{ 0 }
};
#define V_STRUCT 0
#define PROC_STRUCT 1

/* These are imposed strictly for sanity's sake */
#define MINULIMIT 1000
#define MAXULIMIT 100000
	
main(argc, argv)
int argc;
char **argv;
{
	register i;
	register fd;
	register nulimit;
	struct proc p;
	struct user u;
	struct var v;

	nulimit=atoi(argv[1]);
	if(nulimit < MINULIMIT || nulimit > MAXULIMIT)
	{
		fprintf(stderr,"Usage: %s NEWULIMIT (%d < NEWULIMIT < %d)\n",argv[0],MINULIMIT,MAXULIMIT);
		exit(1);
	}
	if(nlist("/unix", nl) == -1)
	{
		perror("Nlist on /unix failed");
		exit(1);
	}
	if((fd = open("/dev/kmem", O_RDWR)) == -1)
	{
		perror("Open of /dev/kmem failed");
		exit(2);
	}
	if((lseek(fd, nl[V_STRUCT].n_value, 0)) == -1)
	{
		perror("Lseek on v struct failed");
		exit(3);
	}
	if(read(fd, &v, sizeof(v)) != sizeof(v))
	{
		perror("Read of v struct failed");
		exit(4);
	}
	if((lseek(fd, nl[PROC_STRUCT].n_value, 0)) == -1)
	{
		perror("Lseek on proc struct failed");
		exit(3);
	}
	for(i = 0 ; i < v.v_proc ; i++)
	{
		if(read(fd, &p, sizeof(p)) != sizeof(p))
		{
			perror("Read of proc struct failed");
			exit(4);
		}
		if(p.p_pid == 1)
			break;
	}
	if(p.p_pid != 1) /* If we can't find init, we're in sad shape! */
	{
		fprintf(stderr,"Can't find init in proc table!\n");
		exit(1);
	}
	if(!(p.p_flag & SLOAD || p.p_flag & SSPART))
	{
		/* If this happens, type 'init q' to force init to be
		   swapped back in.  Then re-run this program		*/
		fprintf(stderr,"Init is swapped, can't change ulimit\n");
		exit(3);
	}
	if(lseek(fd, p.p_ubseg.wd2.address, 0) == -1)
	{
		perror("Lseek for read of init's ublock failed");
		exit(5);
	}
	if(read(fd, &u, sizeof(u)) != sizeof(u))
	{
		perror("Read of init's ublock failed");
		exit(4);
	}
	if(u.u_limit < MINULIMIT || u.u_limit > MAXULIMIT)
	{
		fprintf(stderr,"Init's ulimit currently is %d (should be > %d and < %d -- giving up!\n",u.u_limit,MINULIMIT,MAXULIMIT);
		exit(2);
	}
	printf("Old ulimit = %d\n",u.u_limit);
	printf("New ulimit = %d\n",nulimit);
	u.u_limit=nulimit;
	if(lseek(fd, p.p_ubseg.wd2.address, 0) == -1)
	{
		perror("Lseek for write of init's ublock failed");
		exit(5);
	}
	if(write(fd, &u, sizeof(u)) != sizeof(u))
	{
		perror("Write of init's ublock failed");
		exit(4);
	}
	close(fd);
}
----------cut here--------
-- 
Theodore Hope
School of Information & Computer Science, Georgia Tech, Atlanta GA 30332
CSNet:	hope at gatech		ARPA:	Hope%GATech.CSNet @ CSNet-Relay.ARPA
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