On Mon, May 16, 2022 at 05:33:21PM -0700, Andrew Morton wrote:
> On Mon, 9 May 2022 16:43:30 +0900 Jaewon Kim <jaewon31.kim@xxxxxxxxxxx> wrote:
>
> > The page extension can be prepared for each section. But if the first
> > page is not valid, the page extension for the section was not
> > initialized though there were many other valid pages within the section.
What do you mean by "first page [in a section] is not valid"?
In recent kernels all struct pages in any section should be valid and
properly initialized.
> > To support the page extension for all sections, refer to memblock memory
> > regions. If the page is valid use the nid from pfn_to_nid, otherwise use
> > the previous nid.
> >
> > Also this pagech changed log to include total sections and a section
> > size.
> >
> > i.e.
> > allocated 100663296 bytes of page_ext for 64 sections (1 section : 0x8000000)
>
> Cc Joonsoo, who wrote this code.
> Cc Mike, for memblock.
>
> Thanks.
>
> >
> > diff --git a/mm/page_ext.c b/mm/page_ext.c
> > index 2e66d934d63f..506d58b36a1d 100644
> > --- a/mm/page_ext.c
> > +++ b/mm/page_ext.c
> > @@ -381,41 +381,43 @@ static int __meminit page_ext_callback(struct notifier_block *self,
> > void __init page_ext_init(void)
> > {
> > unsigned long pfn;
> > - int nid;
> > + int nid = 0;
> > + struct memblock_region *rgn;
> > + int nr_section = 0;
> > + unsigned long next_section_pfn = 0;
> >
> > if (!invoke_need_callbacks())
> > return;
> >
> > - for_each_node_state(nid, N_MEMORY) {
> > + /*
> > + * iterate each memblock memory region and do not skip a section having
> > + * !pfn_valid(pfn)
> > + */
> > + for_each_mem_region(rgn) {
> > unsigned long start_pfn, end_pfn;
> >
> > - start_pfn = node_start_pfn(nid);
> > - end_pfn = node_end_pfn(nid);
> > - /*
> > - * start_pfn and end_pfn may not be aligned to SECTION and the
> > - * page->flags of out of node pages are not initialized. So we
> > - * scan [start_pfn, the biggest section's pfn < end_pfn) here.
> > - */
> > + start_pfn = (unsigned long)(rgn->base >> PAGE_SHIFT);
> > + end_pfn = start_pfn + (unsigned long)(rgn->size >> PAGE_SHIFT);
> > +
> > + if (start_pfn < next_section_pfn)
> > + start_pfn = next_section_pfn;
> > +
> > for (pfn = start_pfn; pfn < end_pfn;
> > pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
> >
> > - if (!pfn_valid(pfn))
> > - continue;
> > - /*
> > - * Nodes's pfns can be overlapping.
> > - * We know some arch can have a nodes layout such as
> > - * -------------pfn-------------->
> > - * N0 | N1 | N2 | N0 | N1 | N2|....
> > - */
> > - if (pfn_to_nid(pfn) != nid)
> > - continue;
> > + if (pfn_valid(pfn))
> > + nid = pfn_to_nid(pfn);
> > + nr_section++;
> > if (init_section_page_ext(pfn, nid))
> > goto oom;
> > cond_resched();
> > }
> > + next_section_pfn = pfn;
> > }
> > +
> > hotplug_memory_notifier(page_ext_callback, 0);
> > - pr_info("allocated %ld bytes of page_ext\n", total_usage);
> > + pr_info("allocated %ld bytes of page_ext for %d sections (1 section : 0x%x)\n",
> > + total_usage, nr_section, (1 << SECTION_SIZE_BITS));
> > invoke_init_callbacks();
> > return;
> >
> > --
> > 2.17.1
> >
--
Sincerely yours,
Mike.
