Date: Thu, 9 Mar 2000 18:51:38 -0800 (PST) From: Bhishan Hemrajani <bhishan@cytosine.dhs.org> To: lists@efinley.com Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Code that crashes 3.4-Stable Message-ID: <200003100251.SAA05266@cytosine.dhs.org> In-Reply-To: <38c85e65.27328632@mail.afnetinc.com> from Elliot Finley at "Mar 10, 2000 02:47:19 am"
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It does work when there are no limits on the users.
I recommend that everyone audits their users using /etc/login.conf.
I have my users limited to 32 processes, and 16m per process.
It didn't crash my system when I was logged in as a limited user.
--bhishan
P.S, after editing /etc/login.conf you have to 'cap_mkdb /etc/login.conf'
> I'm in the process of stress testing a system for a program that I'm
> writing. This program will be starting lots of processes, so I wrote
> a short bit a code to test this out.
>
> The machine is 3.4-stable as of a couple of days ago, PII-350 384M
> RAM, and 500M swap. The kernel has MAXUSERS 512, which should give us
> about 8200 process slots. After forking approx. 5100 children
> processes, the machine runs out of RAM, and starts using swap, after
> about 64K of swap is used (as shown by top), the machine freezes
> solid. No core, no logged messages, no socket activity, no messages
> on console, nothing.
>
> If someone can see a problem with the code, I would appreciate some
> pointers. But even if there IS a problem... You shouldn't be able to
> crash the system with a user program running with no privileges.
>
> If I take out the 'sleep(30)' from the child process, then this
> program runs fine, even with the loop counter set to 100,000 (one
> hundred thousand), because the child processes go away fast enough
> that I can only get about 400 of them running at any one time. The
> problem seems to be when the machine runs out of memory, and starts to
> swap.
>
> Here is the code, it was compiled with 'g++ -o test test.c'
> -----------------------------------------------------------
>
> #include <iostream.h>
> #include <sys/types.h>
> #include <sys/wait.h>
> #include <signal.h>
> #include <unistd.h>
> //#include <stdlib.h>
>
> void sig_child(int i)
> {
> int pid;
> int status;
>
> while ( (pid = wait3(&status, WNOHANG, (struct rusage *) 0)) > 0) ;
> }
>
> main()
> {
> cout << "Hello World!" << endl;
>
> void sig_child(int i);
>
> signal(SIGCHLD, sig_child);
>
> int iIsParent;
>
> for(int i = 0; i < 8000; i++) {
> iIsParent = fork();
> if(iIsParent < 0) { cout << "Error Forking!" << endl; }
> if(!iIsParent) {
> cout << "I'm child #" << i << endl;
> sleep(30);
> return 0;
> }
> }
>
> sleep(10);
> cout << "Parent done." << endl;
> return 0;
> }
>
> --
> Elliot (efinley@efinley.com) Weird Science!
>
>
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