Subject: Re: increase default for number of files descriptors per process (was Re: Speeding up "pstat -T")
To: Perry E. Metzger <perry@piermont.com>
From: Andrew Brown <atatat@atatdot.net>
List: tech-kern
Date: 10/07/2003 11:04:26
>> > A machine with 4G of physical memory probably can afford to
>> > let user processes have a bit of a larger default stack size than a
>> > machine with 4M of memory, right?
>>
>> Why should the amount of physical memory have any effect on the
>> default stack size limit of a process?
>
>It is more damaging on a machine with little physical memory for one
>user to take up lots and lots of memory than on a machine with
>plenty. The limits are partially there to prevent certain kinds of
>denial of service.
while that's nominally true, there's still *nothing* preventing me
from doing this:
char *p;
for (p = 0x40000000;
(p = mmap(p, 4096, PROT_READ|PROT_WRITE, MAP_ANON, -1, 0)) != -1;
p += 4096)
*p = '*';
so if had had more stack space, that would reduce to this:
void foo(void) { foo(); }
main() { foo(); }
the latter would merely take longer. oh, and cost more in kvm along
the way. ;-)
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