From: erik quanstrom <quanstro@quanstro.net>
To: 9fans@9fans.net
Subject: Re: [9fans] lowest valid stack address
Date: Tue, 1 Sep 2009 19:49:33 -0400 [thread overview]
Message-ID: <a3d8f244f00be51b2b9f80895be0be93@quanstro.net> (raw)
In-Reply-To: <dd6fe68a0909011622l20f9e6abv2f3ebf75254b3e1e@mail.gmail.com>
On Tue Sep 1 19:24:33 EDT 2009, rsc@swtch.com wrote:
> I believe that the Stack line in /proc/$pid/segment
> tells you the lowest possible stack address, not
> the amount in use right now. I looked in the kernel
> source and tried it in 9vx and it confirms my belief.
> I don't have a Plan 9 kernel to try it on right now,
> so maybe I'm wrong.
>
> Do you have two different /proc/$pid/segment
> with different lowest stack addresses on the Stack line?
evidently i misread /proc/$pid/segment.
and i guess this should have been obvious.
segments don't grow on demand. but inside
a segment, you can have demand zero fill.
aside: from the overcommit vm discussion.
in http://9fans.net/archive/2000/06/634 rob
says that plan 9 doesn't overcommit vm.
what's the history here?
- erik
---
#include <u.h>
#include <libc.h>
enum {
Stack = 15*1024*1024,
};
char *runargv[] = {"/bin/sed", "1q", 0, 0};
void
run(char **argv)
{
switch(fork()){
case -1:
sysfatal("fork: %r");
case 0:
exec(*argv, argv);
sysfatal("exec: %r");
default:
waitpid();
}
}
void
bigstack(void)
{
char big[Stack];
memset(big, 0, sizeof big);
run(runargv);
}
void
main(void)
{
char buf[64];
snprint(buf, sizeof buf, "/proc/%ud/segment", getpid());
runargv[2] = buf;
run(runargv);
bigstack();
exits("");
}
next prev parent reply other threads:[~2009-09-01 23:49 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-01 15:08 erik quanstrom
2009-09-01 16:52 ` cinap_lenrek
2009-09-01 16:55 ` erik quanstrom
2009-09-01 17:47 ` erik quanstrom
2009-09-01 23:22 ` Russ Cox
2009-09-01 23:49 ` erik quanstrom [this message]
2009-09-01 23:59 ` Russ Cox
2009-09-02 0:18 ` Devon H. O'Dell
2009-09-02 8:01 ` Andrés Domínguez
2009-09-02 8:58 ` Gorka Guardiola
2009-09-02 13:32 ` erik quanstrom
2009-09-02 13:28 ` Devon H. O'Dell
2009-09-02 13:35 ` erik quanstrom
2009-09-02 14:17 ` Devon H. O'Dell
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