Re: [PATCH v3 1/2] mm/sparse: add sparse_init_nid()

[Baoquan He <bhe@redhat.com>]

On 07/02/18 at 11:14am, Baoquan He wrote:
> On 07/01/18 at 11:03pm, Pavel Tatashin wrote:
> > > Ah, yes, I misunderstood it, sorry for that.
> > >
> > > Then I have only one concern, for vmemmap case, if one section doesn't
> > > succeed to populate its memmap, do we need to skip all the remaining
> > > sections in that node?
> > 
> > Yes, in sparse_populate_node() we have the following:
> > 
> > 294         for (pnum = pnum_begin; map_index < map_count; pnum++) {
> > 295                 if (!present_section_nr(pnum))
> > 296                         continue;
> > 297                 if (!sparse_mem_map_populate(pnum, nid, NULL))
> > 298                         break;
> > 
> > So, on the first failure, we even stop trying to populate other
> > sections. No more memory to do so.
> 
> This is the thing I worry about. In old sparse_mem_maps_populate_node()
> you can see, when not present or failed to populate, just continue. This
> is the main difference between yours and the old code. The key logic is
> changed here.
> 
Forgot mentioning it's the vervion in mm/sparse-vmemmap.c

> void __init sparse_mem_maps_populate_node(struct page **map_map,
>                                           unsigned long pnum_begin,
>                                           unsigned long pnum_end,
>                                           unsigned long map_count, int nodeid)
> {
> 	...
> 	for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
>                 struct mem_section *ms;
> 
>                 if (!present_section_nr(pnum))
>                         continue;
> 
>                 map_map[pnum] = sparse_mem_map_populate(pnum, nodeid, NULL);
>                 if (map_map[pnum])                                                                                                                
>                         continue;
>                 ms = __nr_to_section(pnum);
>                 pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
>                        __func__);
>                 ms->section_mem_map = 0;
>         }
> 	...
> }
>