mm/memory_hotplug: optimize memory hotplug

During memory hotplugging we traverse struct pages three times:

1. memset(0) in sparse_add_one_section()
2. loop in __add_section() to set do: set_page_node(page, nid); and
   SetPageReserved(page);
3. loop in memmap_init_zone() to call __init_single_pfn()

This patch removes the first two loops, and leaves only loop 3.  All
struct pages are initialized in one place, the same as it is done during
boot.

The benefits:

 - We improve memory hotplug performance because we are not evicting the
   cache several times and also reduce loop branching overhead.

 - Remove condition from hotpath in __init_single_pfn(), that was added
   in order to fix the problem that was reported by Bharata in the above
   email thread, thus also improve performance during normal boot.

 - Make memory hotplug more similar to the boot memory initialization
   path because we zero and initialize struct pages only in one
   function.

 - Simplifies memory hotplug struct page initialization code, and thus
   enables future improvements, such as multi-threading the
   initialization of struct pages in order to improve hotplug
   performance even further on larger machines.

[pasha.tatashin@oracle.com: v5]
  Link: http://lkml.kernel.org/r/20180228030308.1116-7-pasha.tatashin@oracle.com
Link: http://lkml.kernel.org/r/20180215165920.8570-7-pasha.tatashin@oracle.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 18 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3183eb2f579c..a3e2ba4f76bb 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1143,10 +1143,9 @@ 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, bool zero)
+                                unsigned long zone, int nid)
 {
-        if (zero)
-                mm_zero_struct_page(page);
+        mm_zero_struct_page(page);
         set_page_links(page, zone, nid, pfn);
         init_page_count(page);
         page_mapcount_reset(page);
@@ -1160,12 +1159,6 @@ static void __meminit __init_single_page(struct page *page, unsigned long pfn,
 #endif
 }
 
-static void __meminit __init_single_pfn(unsigned long pfn, unsigned long zone,
-                                        int nid, bool zero)
-{
-        return __init_single_page(pfn_to_page(pfn), pfn, zone, nid, zero);
-}
-
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 static void __meminit init_reserved_page(unsigned long pfn)
 {
@@ -1184,7 +1177,7 @@ 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, true);
+        __init_single_page(pfn_to_page(pfn), pfn, zid, nid);
 }
 #else
 static inline void init_reserved_page(unsigned long pfn)
@@ -1501,7 +1494,7 @@ static unsigned long  __init deferred_init_pages(int nid, int zid,
                 } else {
                         page++;
                 }
-                __init_single_page(page, pfn, zid, nid, true);
+                __init_single_page(page, pfn, zid, nid);
                 nr_pages++;
         }
         return (nr_pages);
@@ -5434,6 +5427,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
         pg_data_t *pgdat = NODE_DATA(nid);
         unsigned long pfn;
         unsigned long nr_initialised = 0;
+        struct page *page;
 #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
         struct memblock_region *r = NULL, *tmp;
 #endif
@@ -5486,6 +5480,11 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 #endif
 
 not_early:
+                page = pfn_to_page(pfn);
+                __init_single_page(page, pfn, zone, nid);
+                if (context == MEMMAP_HOTPLUG)
+                        SetPageReserved(page);
+
                 /*
                  * Mark the block movable so that blocks are reserved for
                  * movable at startup. This will force kernel allocations
@@ -5502,15 +5501,8 @@ not_early:
                  * because this is done early in sparse_add_one_section
                  */
                 if (!(pfn & (pageblock_nr_pages - 1))) {
-                        struct page *page = pfn_to_page(pfn);
-
-                        __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,
-                                        context != MEMMAP_HOTPLUG);
                 }
         }
 }