Re: [PATCH 2/6] mm: handle uninitialized numa nodes gracefully

Mike Rapoport
2022-01-27T15:04:29Z

On Thu, Jan 27, 2022 at 03:47:40PM +0100, Michal Hocko wrote:
> On Thu 27-01-22 15:37:23, Mike Rapoport wrote:
> > On Thu, Jan 27, 2022 at 09:53:01AM +0100, Michal Hocko wrote:
> [...]
> > > + if (!node_online(nid)) {
> > > + pr_warn("Node %d uninitialized by the platform. Please report with boot dmesg.\n", nid);
> >
> > Do we assume that platform code must allocate node data for all nodes in
> > the system? Because if we don't this warning is misleading.
>
> At least x86 does that (init_cpu_to_node). Now that you brought that up
> I guess you are right that this could be more misleading than helpful.

I'm not sure if other architectures allocate memoryless nodes, but for sure
only x86 initializes it with free_area_init_memoryless_node().

> What about
> pr_info("Initializing node %d as memoryless\n", nid);
> Is this better?

I think yes.

> > > +
> > > + /* Allocator not initialized yet */
> > > + pgdat = arch_alloc_nodedata(nid);
> > > + if (!pgdat) {
> > > + pr_err("Cannot allocate %zuB for node %d.\n",
> > > + sizeof(*pgdat), nid);
> > > + continue;
> > > + }
> > > + arch_refresh_nodedata(nid, pgdat);
> > > + free_area_init_memoryless_node(nid);
> > > + /*
> > > + * not marking this node online because we do not want to
> > > + * confuse userspace by sysfs files/directories for node
> > > + * without any memory attached to it (see topology_init)
> > > + * The pgdat will get fully initialized when a memory is
> > > + * hotpluged into it by hotadd_init_pgdat
> > > + */
> > > + continue;
> >
> > This can be made slightly more concise if we fall through after
> > arch_refresh_nodedata(), e.g. something like
> >
> > ...
> >
> > arch_refresh_nodedata(nid, pgdat);
> > }
> >
> > pgdat = NODE_DATA(nid);
> > free_area_init_node(nid);
> >
> > /*
> > * Do not mark memoryless node online because we do not want to
> > * confuse userspace by sysfs files/directories for node
> > * without any memory attached to it (see topology_init)
> > * The pgdat will get fully initialized when a memory is
> > * hotpluged into it by hotadd_init_pgdat
> > */
> > if (!pgdat->node_present_pages)
> > continue;
> >
> > but I don't feel strongly about it.
>
> I do not have strong preference either way. Unless this is considered
> better by more people I would stick with what I have.
> --
> Michal Hocko
> SUSE Labs

--
Sincerely yours,
Mike.