Re: [BUG] set_mempolicy(MPOL_INTERLEAV) cause kernel panic

[David Rientjes]

On Tue, 28 Jul 2009, KAMEZAWA Hiroyuki wrote:

> > The nodemask for each task is updated to reflect the removal of a node and 
> > it calls mpol_rebind_mm() with the new nodemask.
> > 
> yes, but _not_ updated at online.
> 

Well, I disagreed that we needed to alter any pre-existing mempolicies for 
MEM_GOING_ONLINE or MEM_ONLINE since it may diverge from the original 
intent of the policy.  MPOL_PREFERRED certain shouldn't change, 
MPOL_INTERLEAVE would be unbalanced, and MPOL_BIND could diverge from 
memory isolation or affinity requirements.

I'd be interested to hear any real world use cases for MEM_ONLINE updating 
of mempolicies.

> What I felt at reading cpuset/mempolicy again is that it's too complex ;)
> The 1st question is why mems_allowed which can be 1024bytes when max_node=4096
> is copied per tasks....

The page allocator needs lockless access to mems_allowed.
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