Re: [patch] check cpuset mems_allowed for sys_mbind

[Christoph Lameter <clameter@sgi.com>]

On Wed, 9 May 2007, Ken Chen wrote:

> On 5/9/07, Christoph Lameter <clameter@sgi.com> wrote:
> > > However, mbind shouldn't create discrepancy between what is allowed
> > > and what is promised, especially with MPOL_BIND policy.  Since a
> > > numa-aware app has already gone such a detail to request memory
> > > placement on a specific nodemask, they fully expect memory to be
> > > placed there for performance reason.  If kernel lies about it, we get
> > > very unpleasant performance issue.
> > 
> > How does the kernel lie? The memory is placed given the current cpuset and
> > memory policy restrictions.
> 
> sys_mbind lies.  A task in cpuset that has mems=0-7, it can do
> sys_mbind(MPOL_BIND, 0x100, ...) and such call will return success.

I thought we assume that people know what they are doing if they run such 
NUMA applications?

I do not think there is an easy way out given the current way of managing 
memory policies and allocation constraints.

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