On Tue 30-01-18 10:16:00, Michal Hocko wrote:
> On Tue 30-01-18 14:00:06, Bharata B Rao wrote:
> > Hi,
> >
> > With the latest upstream, I see that memory hotplug is not working
> > as expected. The hotplugged memory isn't seen to increase the total
> > RAM pages. This has been observed with both x86 and Power guests.
> >
> > 1. Memory hotplug code intially marks pages as PageReserved via
> > __add_section().
> > 2. Later the struct page gets cleared in __init_single_page().
> > 3. Next online_pages_range() increments totalram_pages only when
> > PageReserved is set.
>
> You are right. I have completely forgot about this late struct page
> initialization during onlining. memory hotplug really doesn't want
> zeroying. Let me think about a fix.
Could you test with the following please? Not an act of beauty but
we are initializing memmap in sparse_add_one_section for memory
hotplug. I hate how this is different from the initialization case
but there is quite a long route to unify those two... So a quick
fix should be as follows.
---
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6129f989223a..97a1d7e96110 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1178,9 +1178,10 @@ static void free_one_page(struct zone *zone,
}
static void __meminit __init_single_page(struct page *page, unsigned long pfn,
- unsigned long zone, int nid)
+ unsigned long zone, int nid, bool zero)
{
- mm_zero_struct_page(page);
+ if (zero)
+ mm_zero_struct_page(page);
set_page_links(page, zone, nid, pfn);
init_page_count(page);
page_mapcount_reset(page);
@@ -1195,9 +1196,9 @@ static void __meminit __init_single_page(struct page
*page, unsigned long pfn,
}
static void __meminit __init_single_pfn(unsigned long pfn, unsigned long zone,
- int nid)
+ int nid, bool zero)
{
- return __init_single_page(pfn_to_page(pfn), pfn, zone, nid);
+ return __init_single_page(pfn_to_page(pfn), pfn, zone, nid, zero);
}
#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
@@ -1218,7 +1219,7 @@ static void __meminit init_reserved_page(unsigned long
pfn)
if (pfn >= zone->zone_start_pfn && pfn < zone_end_pfn(zone))
break;
}
- __init_single_pfn(pfn, zid, nid);
+ __init_single_pfn(pfn, zid, nid, true);
}
#else
static inline void init_reserved_page(unsigned long pfn)
@@ -1535,7 +1536,7 @@ static unsigned long __init deferred_init_pages(int nid,
int zid,
} else {
page++;
}
- __init_single_page(page, pfn, zid, nid);
+ __init_single_page(page, pfn, zid, nid, true);
nr_pages++;
}
return (nr_pages);
@@ -5404,11 +5405,13 @@ void __meminit memmap_init_zone(unsigned long size, int
nid, unsigned long zone,
if (!(pfn & (pageblock_nr_pages - 1))) {
struct page *page = pfn_to_page(pfn);
- __init_single_page(page, pfn, zone, nid);
+ __init_single_page(page, pfn, zone, nid,
+ context != MEMMAP_HOTPLUG);
set_pageblock_migratetype(page, MIGRATE_MOVABLE);
cond_resched();
} else {
- __init_single_pfn(pfn, zone, nid);
+ __init_single_pfn(pfn, zone, nid,
+ context != MEMMAP_HOTPLUG);
}
}
}
--
Michal Hocko
SUSE Labs
