Date: Fri, 10 Jul 1998 02:22:56 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: archie@whistle.com (Archie Cobbs) Cc: drosih@rpi.edu, freebsd-current@FreeBSD.ORG Subject: Re: Rate limit for system calls to prevent denial of service attacks? Message-ID: <199807100222.TAA10893@usr09.primenet.com> In-Reply-To: <199807091815.LAA09514@bubba.whistle.com> from "Archie Cobbs" at Jul 9, 98 11:15:28 am
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> Why would 100 processes doing
>
> main(){while(1) getpid();}
>
> be accounted for any differently than 100 processes doing
>
> main(){while(1) /* infinite loop in user mode */;}
>
> ? Or am I misunderstanding something.
1) Accounting is by process.
2) The issue is competition for quantum, and the current
scheduler algorithm fails to decrease virtual priorities
sufficiently fast if there is a large number of quanta
between when you were last scheduled and when you are
next scheduled. For the large number of processes that
result from "for(;;) { fork(); }", this is a degenerate
case for teh scheduling algorithm.
Terry Lambert
terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.
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