Re: [PATCH/RFC] Migrate-on-fault prototype 0/5 V0.1 - Overview

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

On Thu, 2006-03-09 at 11:42 -0800, Christoph Lameter wrote:
> On Thu, 9 Mar 2006, Lee Schermerhorn wrote:
> 
> > I'm wondering if applications keep changing the policy as you describe
> > to "finesse" the system--e.g., because they don't have fine enough
> > control over the policies.  Perhaps I read it wrong, but it appears to
> > me that we can't set the policy for subranges of a vm area.  So maybe
> 
> We can set the policies for subranges. See mempolicy.c

Yow!  I see.  We split the vma.  I did look at this a while back to see
if I needed to worry about different policies on subranges of VMAs.
Came away realizing that I did not have to worry because each vma only
has a single policy.  Forgot about the splitting...   Hmmm, isn't a
vm_area_struct a rather heavy-weight policy container?  Oh well, at
least we can't exceed sysctl_max_map_count of them [64K by default] per
task/mm ;-).  And probably only applications on really big systems will
do this to any extent.  

Lee


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