Re: [9fans] protection against resource exhaustion

[Quintile <steve@quintile.net>]

I always thought the best solution for a university system, is to implement the fair share scheduler. thus people can use any resource the want on an idle machine, but a saturated machine splits its load based on rules.

I had this experience when I managed a cray (YMP-El only) and it worked perfectly. it did not limit processes per user, but it could.

similarly ram use and network bandwidth - though this only works per machine.

personally I like erik's idea, though I would make it a boot option.

I would also keep malloc() returning nil on fail, but add emalloc() to libc.
and finally have an environment car that makes emalloc() clas sys fatal)) or abort() - for debug.

Steve





> On 28 Jan 2015, at 06:50, arisawa <arisawa@ar.aichi-u.ac.jp> wrote:
> 
> Hello,
> 
>> nonetheless, i have experience running multi-user plan 9 systems, and users
>> were not usually the issue.
> 
> Eric’s users are all gentleman, all careful people and all skillful programmers.
> If your system is served for university students, you will have different thought.
> 
>> i think you've turned a problem with bounded recovery time into a
>> situation where the recovery code itself will inadvertently dos attack its
>> users.
> 
> in case that a process failed in getting resource such as memory or process, 
> what it should do is very limited: puts out some message and exits.
> this is right behavior.
> I have never seen programs that retry malloc() or fork() until succeed.
> if all processes retry them, the system will get down.
> this is what I have observed in current plan9 kernel.
> 
> if any one has cleaner solution, i.e., a solution that never kill innocent process,
> I want to see it.
> 
>