Re: [PATCH] Use MPOL_PREFERRED for system default policy

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

On Thu, 2007-08-16 at 11:34 -0700, Christoph Lameter wrote:
> On Thu, 16 Aug 2007, Lee Schermerhorn wrote:
> 
> > 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 still have not gotten my head around this one. Lets wait awhile.

Well, it doesn't get much additional testing just sitting in my tree.

I have placed WARN_ON_ONCE() and a fall back to local in the 'default:'
switch cases where I've removed the MPOL_DEFAULT cases.  So, it'll still
have the same behavior while warning us that an MPOL_DEFAULT has snuck
into a struct mempolicy.  There shouldn't be any occurrences of this in
the kernel, once system default policy is changed to MPOL_PREFERRED w/
preferred_node == -1.  I'd sure like to have more testing exposure,
tho'.

Still, if you need more time, please do look at what mpol_new() returns
for MPOL_DEFAULT and how that result gets used.  From my investigations,
system default policy is the only place where MPOL_DEFAULT occurs in a
struct mempolicy.  Well, that and when we return a mempolicy to the kmem
cache--we null out the policy member with MPOL_DEFAULT.  I've "fixed"
that, too.

Later,
Lee

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