Re: [PATCH 1/2] rcfs core patch

[Herbert Poetzl <herbert@13thfloor.at>]

On Fri, Mar 09, 2007 at 12:07:27PM +0300, Kirill Korotaev wrote:
>>  nobody actually cares about a precise accounting and
>>  calculating shares or partitions of whatever resource,
>>  all that matters is that you have a way to prevent a
>>  potential hostile environment from sucking up all your
>>  resources (or even a single one) resulting in a DoS

> This is not true. People care. Reasons:
>   - resource planning
>   - fairness
>   - guarantees

let me make that a little more clear ...

_nobody_ cares wether a shared memory page is
accounted as full page or as fraction of a page
(depending on the number of guests sharing it)
as long as the accounted amount is substracted
correctly when the page is disposed 

so there _is_ a difference between _false_
accounting (which seems what you are referring
to in the next paragraph) and imprecise, but
consistant accounting (which is what I was 
talking about)

best,
Herbert

>   What you talk is about security only. Not the above issues.
>   So good precision is required. If there is no precision at all,
>   security sucks as well and can be exploited, e.g. for CPU
>   schedulers doing an accounting based on jiffies accounting in
>   scheduler_tick() it is easy to build an application consuming
>   90% of CPU, but ~0% from scheduler POV.

> Kirill