Re: quotas [was: thread ids, task ids and subsystems]

[Michal 'hramrach' Suchanek]

On Mon, Apr 14, 2003 at 09:55:32PM +0200, Marcus Brinkmann wrote:
> 
> * The user has all the freedom we can provide without harming security.
> * The user has all the freedom we can provide without harming security.
> * The user has all the freedom we can provide without harming security.
> 
> This means that something like file handles doesn't need to be restricted at
> all.  What needs to be restricted (if at all) is processor time, memory,
> kernel objects, system objects (if they can not indirectly be restricted by
> restricting memory or processor time).
> 

IIRC most quota problems were already discussed specifically for memory.
The protocol for obtaining memory could be probably generealized for any
resource.
I cannot remember any solution for the problem of reclaiming resources, which
is probably the same for all types of resources.


It looks like there are basically two types of resources that a user could
spend:
 - real hardware resources (like memory, cpu time, network bandwidth,
        disk space, ...)
These have to be provided by a priviledged server that can access the hardware
directly. There may be the need for a qouta server anyway since one can have
several network cards and disk drives and perform some sort of load balancing.
The quota server has to be trusted by the hardware server, because it is
useless otherwise. But there is no need for all networking interfaces to use
the same quota server for accounting, for example.

 - some artifical resources that may correspond to system resources indirectly
(ie database transactions, file handles, sound records)
Qoutas on such resoures do not correspond directly to some amount of hardware
resources, they are just some abstraction. But I see no reason why interface
for creating such abstractions cannot be provided.

Another thing regarding quotas comes to my mind: they can be specified as a 
contract on some amount of resources for indefinite time
(ie 20% cpu time, 100MiB disk space) or as a resource limited in time
(ie 3hours of cpu time, 1GiB.day)