Re: cpusets vs. mempolicy and how to get interleaving

[David Rientjes <rientjes@google.com>]

On Sun, 19 Aug 2007, Paul Jackson wrote:

> > 	BTW, a slightly different MPOL_INTERLEAVE implementation would help, 
> > wherein we save the nodemask originally specified by the user and do the 
> > remap from the original nodemask rather than the current nodemask.
> 
> I kinda like this idea; though keep in mind that since I don't use
> mempolicy mechanisms, I am not loosing any sleep over minor(?)
> compatibility breakages.  It would take someone familiar with the
> actual users or usages of MPOL_INTERLEAVE to know if or how much
> this would bite actual users/usages.
> 

Like I've already said, there is absolutely no reason to add a new MPOL 
variant for this case.  As Christoph already mentioned, PF_SPREAD_PAGE 
gets similar results.  So just modify mpol_rebind_policy() so that if 
/dev/cpuset/<cpuset>/memory_spread_page is true, you rebind the 
interleaved nodemask to all nodes in the new nodemask.  That's the 
well-defined cpuset interface for getting an interleaved behavior already.

Let's not create new memory policies that only work for a very specific 
and configurable case when the basic underlying mechanism to that policy 
is already present in the cpuset interface, namely, PF_SPREAD_PAGE.

		David

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