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Subject[PATCH v6 5/5] mm/page_alloc: Introduce free_area_init_core_hotplug
Date
From: Oscar Salvador <osalvador@suse.de>

Currently, whenever a new node is created/re-used from the memhotplug path,
we call free_area_init_node()->free_area_init_core().
But there is some code that we do not really need to run when we are coming
from such path.

free_area_init_core() performs the following actions:

1) Initializes pgdat internals, such as spinlock, waitqueues and more.
2) Account # nr_all_pages and # nr_kernel_pages. These values are used later on
when creating hash tables.
3) Account number of managed_pages per zone, substracting dma_reserved and memmap pages.
4) Initializes some fields of the zone structure data
5) Calls init_currently_empty_zone to initialize all the freelists
6) Calls memmap_init to initialize all pages belonging to certain zone

When called from memhotplug path, free_area_init_core() only performs actions #1 and #4.

Action #2 is pointless as the zones do not have any pages since either the node was freed,
or we are re-using it, eitherway all zones belonging to this node should have 0 pages.
For the same reason, action #3 results always in manages_pages being 0.

Action #5 and #6 are performed later on when onlining the pages:
online_pages()->move_pfn_range_to_zone()->init_currently_empty_zone()
online_pages()->move_pfn_range_to_zone()->memmap_init_zone()

This patch does two things:

First, moves the node/zone initializtion to their own function, so it allows us
to create a small version of free_area_init_core, where we only perform:

1) Initialization of pgdat internals, such as spinlock, waitqueues and more
4) Initialization of some fields of the zone structure data

These two functions are: pgdat_init_internals() and zone_init_internals().

The second thing this patch does, is to introduce free_area_init_core_hotplug(),
the memhotplug version of free_area_init_core():

Currently, we call free_area_init_node() from the memhotplug path.
In there, we set some pgdat's fields, and call calculate_node_totalpages().
calculate_node_totalpages() calculates the # of pages the node has.

Since the node is either new, or we are re-using it, the zones belonging to
this node should not have any pages, so there is no point to calculate this now.

Actually, we re-set these values to 0 later on with the calls to:

reset_node_managed_pages()
reset_node_present_pages()

The # of pages per node and the # of pages per zone will be calculated when
onlining the pages:

online_pages()->move_pfn_range()->move_pfn_range_to_zone()->resize_zone_range()
online_pages()->move_pfn_range()->move_pfn_range_to_zone()->resize_pgdat_range()

Also, with this change, only pgdat_init_internals() and zone_init_internals() should
be kept around after initialization, since they can be called from memory-hotplug
code.
So let us reconvert all the other functions from __meminit to __init, as we do not need
them after initialization:

zero_resv_unavail
set_pageblock_order
calc_memmap_size
free_area_init_core
free_area_init_node

Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
include/linux/memory_hotplug.h | 1 +
include/linux/mm.h | 2 +-
mm/memory_hotplug.c | 16 +++------
mm/page_alloc.c | 78 +++++++++++++++++++++++++++++-------------
4 files changed, 61 insertions(+), 36 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 4e9828cda7a2..34a28227068d 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -319,6 +319,7 @@ static inline int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
static inline void remove_memory(int nid, u64 start, u64 size) {}
#endif /* CONFIG_MEMORY_HOTREMOVE */

+extern void __ref free_area_init_core_hotplug(int nid);
extern int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
void *arg, int (*func)(struct memory_block *, void *));
extern int add_memory(int nid, u64 start, u64 size);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 70edbc3f21a8..90d75e4fcc2a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2012,7 +2012,7 @@ static inline spinlock_t *pud_lock(struct mm_struct *mm, pud_t *pud)

extern void __init pagecache_init(void);
extern void free_area_init(unsigned long * zones_size);
-extern void free_area_init_node(int nid, unsigned long * zones_size,
+extern void __init free_area_init_node(int nid, unsigned long * zones_size,
unsigned long zone_start_pfn, unsigned long *zholes_size);
extern void free_initmem(void);

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 4eb6e824a80c..9eea6e809a4e 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -982,8 +982,6 @@ static void reset_node_present_pages(pg_data_t *pgdat)
static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
{
struct pglist_data *pgdat;
- unsigned long zones_size[MAX_NR_ZONES] = {0};
- unsigned long zholes_size[MAX_NR_ZONES] = {0};
unsigned long start_pfn = PFN_DOWN(start);

pgdat = NODE_DATA(nid);
@@ -1006,8 +1004,11 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)

/* we can use NODE_DATA(nid) from here */

+ pgdat->node_id = nid;
+ pgdat->node_start_pfn = start_pfn;
+
/* init node's zones as empty zones, we don't have any present pages.*/
- free_area_init_node(nid, zones_size, start_pfn, zholes_size);
+ free_area_init_core_hotplug(nid);
pgdat->per_cpu_nodestats = alloc_percpu(struct per_cpu_nodestat);

/*
@@ -1017,18 +1018,11 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
build_all_zonelists(pgdat);

/*
- * zone->managed_pages is set to an approximate value in
- * free_area_init_core(), which will cause
- * /sys/device/system/node/nodeX/meminfo has wrong data.
- * So reset it to 0 before any memory is onlined.
- */
- reset_node_managed_pages(pgdat);
-
- /*
* When memory is hot-added, all the memory is in offline state. So
* clear all zones' present_pages because they will be updated in
* online_pages() and offline_pages().
*/
+ reset_node_managed_pages(pgdat);
reset_node_present_pages(pgdat);

return pgdat;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 56ee8c029759..47cbc0fd1e4c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6142,7 +6142,7 @@ static inline void setup_usemap(struct pglist_data *pgdat, struct zone *zone,
#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE

/* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */
-void __meminit set_pageblock_order(void)
+void __init set_pageblock_order(void)
{
unsigned int order;

@@ -6170,13 +6170,13 @@ void __meminit set_pageblock_order(void)
* include/linux/pageblock-flags.h for the values of pageblock_order based on
* the kernel config
*/
-void __meminit set_pageblock_order(void)
+void __init set_pageblock_order(void)
{
}

#endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */

-static unsigned long __meminit calc_memmap_size(unsigned long spanned_pages,
+static unsigned long __init calc_memmap_size(unsigned long spanned_pages,
unsigned long present_pages)
{
unsigned long pages = spanned_pages;
@@ -6227,19 +6227,8 @@ static void pgdat_init_kcompactd(struct pglist_data *pgdat)
static void pgdat_init_kcompactd(struct pglist_data *pgdat) {}
#endif

-/*
- * Set up the zone data structures:
- * - mark all pages reserved
- * - mark all memory queues empty
- * - clear the memory bitmaps
- *
- * NOTE: pgdat should get zeroed by caller.
- */
-static void __meminit free_area_init_core(struct pglist_data *pgdat)
+static void __meminit pgdat_init_internals(struct pglist_data *pgdat)
{
- enum zone_type j;
- int nid = pgdat->node_id;
-
pgdat_resize_init(pgdat);

pgdat_init_numabalancing(pgdat);
@@ -6252,7 +6241,54 @@ static void __meminit free_area_init_core(struct pglist_data *pgdat)
pgdat_page_ext_init(pgdat);
spin_lock_init(&pgdat->lru_lock);
lruvec_init(node_lruvec(pgdat));
+}
+
+static void __meminit zone_init_internals(struct zone *zone, enum zone_type idx, int nid,
+ unsigned long remaining_pages)
+{
+ zone->managed_pages = remaining_pages;
+ zone_set_nid(zone, nid);
+ zone->name = zone_names[idx];
+ zone->zone_pgdat = NODE_DATA(nid);
+ spin_lock_init(&zone->lock);
+ zone_seqlock_init(zone);
+ zone_pcp_init(zone);
+}
+
+/*
+ * Set up the zone data structures
+ * - init pgdat internals
+ * - init all zones belonging to this node
+ *
+ * NOTE: this function is only called during memory hotplug
+ */
+#ifdef CONFIG_MEMORY_HOTPLUG
+void __ref free_area_init_core_hotplug(int nid)
+{
+ enum zone_type z;
+ pg_data_t *pgdat = NODE_DATA(nid);
+
+ pgdat_init_internals(pgdat);
+ for (z = 0; z < MAX_NR_ZONES; z++)
+ zone_init_internals(&pgdat->node_zones[z], z, nid, 0);
+}
+#endif
+
+/*
+ * Set up the zone data structures:
+ * - mark all pages reserved
+ * - mark all memory queues empty
+ * - clear the memory bitmaps
+ *
+ * NOTE: pgdat should get zeroed by caller.
+ * NOTE: this function is only called during early init.
+ */
+static void __init free_area_init_core(struct pglist_data *pgdat)
+{
+ enum zone_type j;
+ int nid = pgdat->node_id;

+ pgdat_init_internals(pgdat);
pgdat->per_cpu_nodestats = &boot_nodestats;

for (j = 0; j < MAX_NR_ZONES; j++) {
@@ -6300,13 +6336,7 @@ static void __meminit free_area_init_core(struct pglist_data *pgdat)
* when the bootmem allocator frees pages into the buddy system.
* And all highmem pages will be managed by the buddy system.
*/
- zone->managed_pages = freesize;
- zone_set_nid(zone, nid);
- zone->name = zone_names[j];
- zone->zone_pgdat = pgdat;
- spin_lock_init(&zone->lock);
- zone_seqlock_init(zone);
- zone_pcp_init(zone);
+ zone_init_internals(zone, j, nid, freesize);

if (!size)
continue;
@@ -6382,7 +6412,7 @@ static inline void pgdat_set_deferred_range(pg_data_t *pgdat)
static inline void pgdat_set_deferred_range(pg_data_t *pgdat) {}
#endif

-void __meminit free_area_init_node(int nid, unsigned long *zones_size,
+void __init free_area_init_node(int nid, unsigned long *zones_size,
unsigned long node_start_pfn,
unsigned long *zholes_size)
{
@@ -6421,7 +6451,7 @@ void __meminit free_area_init_node(int nid, unsigned long *zones_size,
* may be accessed (for example page_to_pfn() on some configuration accesses
* flags). We must explicitly zero those struct pages.
*/
-void __meminit zero_resv_unavail(void)
+void __init zero_resv_unavail(void)
{
phys_addr_t start, end;
unsigned long pfn;
--
2.13.6
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