linux-kernel - Re: [patch 2/4] mempolicy: support optional mode flags

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Date:	Mon, 11 Feb 2008 11:34:03 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Lee Schermerhorn <Lee.Schermerhorn@...com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Jackson <pj@....com>,
	Christoph Lameter <clameter@....com>, Andi Kleen <ak@...e.de>,
	Mel Gorman <mel@....ul.ie>, linux-kernel@...r.kernel.org
Subject: Re: [patch 2/4] mempolicy: support optional mode flags

On Mon, 11 Feb 2008, Lee Schermerhorn wrote:

> These patches look good--well, interesting, anyway.  I'm "off on
> assignment" this week, so I won't get to review in detail, merge and
> test them until next...   
> 

If, by "interesting", you mean that they give the most power to the user 
in setting up their mempolicies than they have ever had before, then I 
agree.

> This helper functions introduced by this patch are similar in nature
> [but go further] to one I introduced in the reference counting cleanup
> RFC [http://marc.info/?l=linux-mm&m=119697614520515&w=4] I posted a
> while back.  I've been holding these cleanup patches until Andrew starts
> accepting this sort of thing again.  I have my series based atop Mel
> Gorman's [added to cc] "two zonelist" series, as it depends on removing
> the custom zonelist from the mempolicy.
> 

If my helper functions are similar to yours then basing either of our 
patchsets on top of the other should not be difficult.

> We need to sort out with Andrew, Mel, Paul, ... the order in which these
> interdependent changes go in.  Given such an order, I'm willing to merge
> them all up, test them, and post them [after running checkpatch, of
> course].
> 

Thanks for volunteering to test the changes.  I don't know how many 
patchsets are currently outstanding that touch mempolicies.  So far we 
have mine and the refcounting cleanup of yours that you mentioned.

I think the best way of dealing with it would be for the author of 
whatever patchset is merged second to rebase off the current -mm just like 
I based this entire patchset on your V3 contextualize_policy() patch from 
a couple days ago.

> One other thing:  In the recent mempolicy patch to "silently restrict
> nodemask], I mentioned the issue with regards to whether and when to
> "contextualize" tmpfs/hugetlbfs policies--if/when we fold
> mpol_check_policy() into mpol_new(), as you suggested.  Once we can
> agree on the desired semantics, I had been thinking that an additional
> mode flag could be added to policies obtained from the superblock, and
> passed via mpol_shared_policy_init() [which calls mpol_new()] could be
> used for this purpose.  Your change here seems to lay the foundation for
> implementing that.
> 

My patchset already supports contextualized tmpfs mempolicies with a 
template for how to specify them (see patch 4 in this series for the 
documentation update).  For example, mpol=interleave:1-3 is the equivalent 
of MPOL_INTERLEAVE over nodes 1-3 while mpol=interleave=static:1-3 is the
equivalent of MPOL_INTERLEAVE | MPOL_F_STATIC_NODES.

		David
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