Re: Minutes from Feb 21 LSE Call

Benjamin LaHaise
2003-02-24T01:32:27Z

On Sun, Feb 23, 2003 at 10:28:04AM -0700, Eric W. Biederman wrote:
> The problem. There is no upper bound to how many rmap
> entries there can be at one time. And the unbounded
> growth can overwhelm a machine.

Eh? By that logic there's no bound to the number of vmas that can exist
at a given time. But there is a bound on the number that a single process
can force the system into using, and that limit also caps the number of
rmap entries the process can bring into existance. Virtual address space
is not free, and there are already mechanisms in place to limit it which,
given that the number of rmap entries are directly proportion to the amount
of virtual address space in use, probably need proper configuration.

> The goal is to provide an overall system cap on the number
> of rmap entries.

No, the goal is to have a stable system under a variety of workloads that
performs well. User exploitable worst case behaviour is a bad idea. Hybrid
solves that at the expense of added complexity.

-ben
--
Don't email: aart@kvack.org