Re: + memory-hotplug-fix-kswapd-looping-forever-problem-fix-fix.patch added to -mm tree

[Tejun Heo <tj@kernel.org>]

(cc'ing Yinghai, hi!)

Hello,

On Thu, Jul 19, 2012 at 09:10:02AM +0900, Minchan Kim wrote:
> On Wed, Jul 18, 2012 at 02:38:10PM -0700, Andrew Morton wrote:
> > On Wed, 18 Jul 2012 10:22:00 +0900
> > Minchan Kim <minchan@kernel.org> wrote:
> > 
> > > > 
> > > > Is this really necessary?  Does the zone start out all-zeroes?  If not, can we
> > > > make it do so?
> > > 
> > > Good point.
> > > It can remove zap_zone_vm_stats and zone->flags = 0, too.
> > > More important thing is that we could remove adding code to initialize
> > > zero whenever we add new field to zone. So I look at the code.
> > > 
> > > In summary, IMHO, all is already initialie zero out but we need double
> > > check in mips.
> > > 
> > 
> > Well, this is hardly a performance-critical path.  So rather than
> > groveling around ensuring that each and every architectures does the
> > right thing, would it not be better to put a single memset() into core
> > MM if there is an appropriate place?
> 
> I think most good place is free_area_init_node but at a glance,
> bootmem_data is set up eariler than free_area_init_node so shouldn't we
> keep that pointer still?

I don't think zapping node_data that late is a good idea.  It's used
from very early in the boot and its usage during early boot is fairly
platform dependent.  Dunno whether there's a good solution for this.
Maybe trigger warning if some fields which have to be zero aren't?

Thanks.

-- 
tejun

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