Re: [PATCH 4/6] Use two zonelist that are filtered by GFP mask

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 27 Feb 2008 16:47:34 -0500
Lee Schermerhorn <lee.schermerhorn@hp.com> wrote:

> +/* Returns the first zone at or below highest_zoneidx in a zonelist */
> +static inline struct zone **first_zones_zonelist(struct zonelist *zonelist,
> +					enum zone_type highest_zoneidx)
> +{
> +	struct zone **z;
> +
> +	/* Find the first suitable zone to use for the allocation */
> +	z = zonelist->zones;
> +	while (*z && zone_idx(*z) > highest_zoneidx)
> +		z++;
> +
> +	return z;
> +}
> +
> +/* Returns the next zone at or below highest_zoneidx in a zonelist */
> +static inline struct zone **next_zones_zonelist(struct zone **z,
> +					enum zone_type highest_zoneidx)
> +{
> +	/* Find the next suitable zone to use for the allocation */
> +	while (*z && zone_idx(*z) > highest_zoneidx)
> +		z++;
> +
> +	return z;
> +}
> +
> +/**
> + * for_each_zone_zonelist - helper macro to iterate over valid zones in a zonelist at or below a given zone index
> + * @zone - The current zone in the iterator
> + * @z - The current pointer within zonelist->zones being iterated
> + * @zlist - The zonelist being iterated
> + * @highidx - The zone index of the highest zone to return
> + *
> + * This iterator iterates though all zones at or below a given zone index.
> + */
> +#define for_each_zone_zonelist(zone, z, zlist, highidx) \
> +	for (z = first_zones_zonelist(zlist, highidx), zone = *z++;	\
> +		zone;							\
> +		z = next_zones_zonelist(z, highidx), zone = *z++)
> +

omygawd will that thing generate a lot of code!

It has four call sites in mm/oom_kill.c and the overall patchset increases
mm/oom_kill.o's text section (x86_64 allmodconfig) from 3268 bytes to 3845.

vmscan.o and page_alloc.o also grew a lot.  otoh total vmlinux bloat from
the patchset is only around 700 bytes, so I expect that with a little less
insanity we could actually get an aggregate improvement here.

Some of the inlining in mmzone.h is just comical.  Some of it is obvious
(first_zones_zonelist) and some of it is less obvious (pfn_present).

I applied these for testing but I really don't think we should be merging
such easily-fixed regressions into mainline.  Could someone please take a
look at de-porking core MM?


Also, I switched all your Tested-by:s to Signed-off-by:s.  You were on the
delivery path, so s-o-b is the appropriate tag.  I would like to believe
that Signed-off-by: implies Tested-by: anyway (rofl).

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