Re: [PATCH 2.6.17-rc1-mm1 2/6] Migrate-on-fault - check for misplaced page

[Lee Schermerhorn <Lee.Schermerhorn@hp.com>]

On Wed, 2006-04-12 at 09:43 -0700, Paul Jackson wrote:
> Christoph, respnonding to Lee:
> > > +			/*
> > > +			 * allows binding to multiple nodes.
> > > +			 * use current page if in zonelist,
> > > +			 * else select first allowed node
> > > +			 */
> > > +			mems = &pol->cpuset_mems_allowed;
> > > +			...
> > 
> > Hmm.... Checking for the current node in memory policy? How does this 
> > interact with cpuset constraints?
> 
> The per-mempolicy 'cpuset_mems_allowed' does not specify the nodes to
> which the task is bound, but rather the nodes to which the mempolicy is
> relative.  No code except the mempolicy rebinding code should be using
> the mempolicy->cpuset_mems_allowed field.
> 
> The proper way to check if a zone is allowed by cpusets appears
> in several places in the files mm/page_alloc.c, mm/vmscan.c, and
> mm/hugetlb.c.

Thanks, Paul.  But, I wonder, do I even need to do this check at all?
I just found the node in the policy's nodelist after having done a
cpuset_update_task_memory_state().  Looks like updating the task
memory state refreshes the policy zonelist, so it should only have nodes
valid in the cpuset.  Is this correct?

If so, I can just drop that check...

Lee


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