Re: [PATCH] Use MPOL_PREFERRED for system default policy

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

On Tue, 2007-08-14 at 16:22 -0400, Lee Schermerhorn wrote:
> On Tue, 2007-08-14 at 16:09 -0400, Lee Schermerhorn wrote:
> > On Tue, 2007-08-14 at 12:51 -0700, Christoph Lameter wrote:
> > > On Tue, 14 Aug 2007, Lee Schermerhorn wrote:
> > > 
> > > > Now, system default policy, except during boot, is "local 
> > > > allocation".  By using the MPOL_PREFERRED mode with a negative
> > > > value of preferred node for system default policy, MPOL_DEFAULT
> > > > will never occur in the 'policy' member of a struct mempolicy.
> > > > Thus, we can remove all checks for MPOL_DEFAULT when converting
> > > > policy to a node id/zonelist in the allocation paths.
> > > 
> > > Isnt it possible to set a task policy or VMA policy to MPOL_DEFAULT 
> > > through the API? For the VMA policy this would mean fall back to task 
> > > policy. Is that still possible?
> > 
> > No.  mpol_new() returns NULL if policy==MPOL_DEFAULT, so you end up just
> > deleting any existing task policy and replacing it with a NULL pointer.
> > This is pretty cool, I think.  I have checked back, but Andi may have
>                                    ^^^^ haven't!
> > done this from day 1.
> > 

Christoph, Andi:

Given that the mem policy does the right thing with this patch, can we
merge it?  I think it cleans up the mem policy concepts to have
MPOL_DEFAULT mean "use default policy for this context/scope" rather
than have an additional allocation behavior of its own.

I'll update the man pages as well, once you've had a chance to review
the current patches that Michael is holding.

Lee

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