Re: [RFC] CPU hard limits

[Srivatsa Vaddagiri]

On Fri, Jun 05, 2009 at 01:53:15AM -0700, Paul Menage wrote:
> This claim (and the subsequent long thread it generated on how limits
> can provide guarantees) confused me a bit.
> 
> Why do we need limits to provide guarantees when we can already
> provide guarantees via shares?

I think the interval over which we need guarantee matters here. Shares
can generally provide guaranteed share of resource over longer (sometimes
minutes) intervals. For high-priority bursty workloads, the latency in 
achieving guaranteed resource usage matters. By having hard-limits, we are 
"reserving" (potentially idle) slots where the high-priority group can run and 
claim its guaranteed share almost immediately.

- vatsa
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