On 23.02.21 10:48, Mike Rapoport wrote:
On Tue, Feb 23, 2021 at 09:04:19AM +0100, David Hildenbrand wrote:
On 22.02.21 11:57, Mike Rapoport wrote:
From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
There could be struct pages that are not backed by actual physical memory.
This can happen when the actual memory bank is not a multiple of
SECTION_SIZE or when an architecture does not register memory holes
reserved by the firmware as memblock.memory.
Such pages are currently initialized using init_unavailable_mem() function
that iterates through PFNs in holes in memblock.memory and if there is a
struct page corresponding to a PFN, the fields of this page are set to
default values and it is marked as Reserved.
init_unavailable_mem() does not take into account zone and node the page
belongs to and sets both zone and node links in struct page to zero.
Before commit 73a6e474cb37 ("mm: memmap_init: iterate over memblock regions
rather that check each PFN") the holes inside a zone were re-initialized
during memmap_init() and got their zone/node links right. However, after
that commit nothing updates the struct pages representing such holes.
On a system that has firmware reserved holes in a zone above ZONE_DMA, for
instance in a configuration below:
# grep -A1 E820 /proc/iomem
7a17b000-7a216fff : Unknown E820 type
7a217000-7bffffff : System RAM
unset zone link in struct page will trigger
VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);
because there are pages in both ZONE_DMA32 and ZONE_DMA (unset zone link
in struct page) in the same pageblock.
Interleave initialization of the unavailable pages with the normal
initialization of memory map, so that zone and node information will be
properly set on struct pages that are not backed by the actual memory.
With this change the pages for holes inside a zone will get proper
zone/node links and the pages that are not spanned by any node will get
links to the adjacent zone/node.
Does this include pages in the last section has handled by ...
...
- /*
- * Early sections always have a fully populated memmap for the whole
- * section - see pfn_valid(). If the last section has holes at the
- * end and that section is marked "online", the memmap will be
- * considered initialized. Make sure that memmap has a well defined
- * state.
- */
- pgcnt += init_unavailable_range(PFN_DOWN(next),
- round_up(max_pfn, PAGES_PER_SECTION));
-
^ this code?
Or how is that case handled now?
Hmm, now it's clamped to node_end_pfn/zone_end_pfn, so in your funny example with
-object memory-backend-ram,id=bmem0,size=4160M \
-object memory-backend-ram,id=bmem1,size=4032M \
this is not handled :(
But it will be handled with this on top:
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 29bbd08b8e63..6c9b490f5a8b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6350,9 +6350,12 @@ void __meminit __weak memmap_init_zone(struct zone *zone)
hole_pfn = end_pfn;
}
- if (hole_pfn < zone_end_pfn)
- pgcnt += init_unavailable_range(hole_pfn, zone_end_pfn,
+#ifdef CONFIG_SPARSEMEM
+ end_pfn = round_up(zone_end_pfn, PAGES_PER_SECTION);
+ if (hole_pfn < end_pfn)
+ pgcnt += init_unavailable_range(hole_pfn, end_pfn,
zone_id, nid);
+#endif
if (pgcnt)
pr_info(" %s zone: %lld pages in unavailable ranges\n",
Also, just wondering, will PFN 0 still get initialized?
--
Thanks,
David / dhildenb
