Re: [PATCH 6/6] Filter based on a nodemask as well as a gfp_mask

[Mel Gorman <mel@csn.ul.ie>]

On (29/02/08 11:59), KAMEZAWA Hiroyuki didst pronounce:
> On Wed, 27 Feb 2008 16:47:47 -0500
> Lee Schermerhorn <lee.schermerhorn@hp.com>, Mel Gorman <mel@csn.ul.ie> wrote:
> 
> > [PATCH 6/6] Filter based on a nodemask as well as a gfp_mask
> > 
> > V11r3 against 2.6.25-rc2-mm1
> > 
> > The MPOL_BIND policy creates a zonelist that is used for allocations
> > controlled by that mempolicy. As the per-node zonelist is already being
> > filtered based on a zone id, this patch adds a version of __alloc_pages()
> > that takes a nodemask for further filtering. This eliminates the need
> > for MPOL_BIND to create a custom zonelist.
> > 
> > A positive benefit of this is that allocations using MPOL_BIND now use the
> > local node's distance-ordered zonelist instead of a custom node-id-ordered
> > zonelist.  I.e., pages will be allocated from the closest allowed node with
> > available memory.
> > 
> > Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> > Acked-by: Christoph Lameter <clameter@sgi.com>
> > Tested-by:  Lee Schermerhorn <lee.schermerhorn@hp.com>
> > 
> 
> Thank you! I like this very much.
> Next step is maybe to pass nodemask to try_to_free_pages().
> 

Not a bad plan. I will visit it after the text bloat is reduced a bit.
Currently each usage of for_each_zone_zonelist_nodemask() adds a bit too
much.

> BTW, cpuset memory limitation by nodemask has the same kind of feature.
> But it seems cpuset_zone_allowed_soft/hardwall() has extra checks for system
> sanity. 
> 
> Could you import them ? maybe like this
> ==
> void __alloc_pages_internal(gfp_t gfp_mask, unsigned int order,
> +			struct zonelist *zonelist, nodemask_t *nodemask))
> {
> 	if (nodemask) {
> 		if (unlikely(test_thread_flag(TIF_MEMDIE)))
> 	                nodemask = NULL;
> 		if ((gfp_mask & __GFP_HARDWALL)
>                      && (unlikely(test_thread_flag(TIF_MEMDIE)))
> 			nodemask = NULL;
> 	}
> }
> ==
> (I don't think above is clean.)

I get the idea, I'll check it out and see.

Thanks

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

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