Re: [PATCH] mm: Fix comment for NODEMASK_ALLOC
From: Oscar Salvador
Date: Tue Aug 21 2018 - 08:58:52 EST
On Tue, Aug 21, 2018 at 02:51:56PM +0200, Michal Hocko wrote:
> On Tue 21-08-18 14:30:24, Oscar Salvador wrote:
> > On Tue, Aug 21, 2018 at 02:17:34PM +0200, Michal Hocko wrote:
> > > We do have CONFIG_NODES_SHIFT=10 in our SLES kernels for quite some
> > > time (around SLE11-SP3 AFAICS).
> > >
> > > Anyway, isn't NODES_ALLOC over engineered a bit? Does actually even do
> > > larger than 1024 NUMA nodes? This would be 128B and from a quick glance
> > > it seems that none of those functions are called in deep stacks. I
> > > haven't gone through all of them but a patch which checks them all and
> > > removes NODES_ALLOC would be quite nice IMHO.
> > No, maximum we can get is 1024 NUMA nodes.
> > I checked this when writing another patch , and since having gone
> > through all archs Kconfigs, CONFIG_NODES_SHIFT=10 is the limit.
> > NODEMASK_ALLOC gets only called from:
> > - unregister_mem_sect_under_nodes() (not anymore after )
> > - __nr_hugepages_store_common (This does not seem to have a deep stack, we could use a normal nodemask_t)
> > But is also used for NODEMASK_SCRATCH (mainly used for mempolicy):
> mempolicy code should be a shallow stack as well. Mostly the syscall
Ok, then I could give it a try and see if we can get rid of NODEMASK_ALLOC in there