Re: [RFC] CPU hard limits

Srivatsa Vaddagiri
2009-06-05T11:32:34Z

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