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>

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 92b00a7..7a3a580 100644 (file)
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -407,6 +407,8 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, int nid,
 
        if (!mem_blk)
                return -EFAULT;
+
+       mem_blk->nid = nid;
        if (!node_online(nid))
                return 0;
 

diff --git a/include/linux/memory.h b/include/linux/memory.h
index 9f8cd85..31ca3e2 100644 (file)
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -33,6 +33,7 @@ struct memory_block {
        void *hw;                       /* optional pointer to fw/hw data */
        int (*phys_callback)(struct memory_block *);
        struct device dev;
+       int nid;                        /* NID for this memory block */
 };
 
 int arch_get_memory_phys_device(unsigned long start_pfn);

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 477e183..6a9ba14 100644 (file)
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -250,7 +250,6 @@ static int __meminit __add_section(int nid, unsigned long phys_start_pfn,
                struct vmem_altmap *altmap, bool want_memblock)
 {
        int ret;
-       int i;
 
        if (pfn_valid(phys_start_pfn))
                return -EEXIST;
@@ -259,23 +258,6 @@ static int __meminit __add_section(int nid, unsigned long phys_start_pfn,
        if (ret < 0)
                return ret;
 
-       /*
-        * Make all the pages reserved so that nobody will stumble over half
-        * initialized state.
-        * FIXME: We also have to associate it with a node because page_to_nid
-        * relies on having page with the proper node.
-        */
-       for (i = 0; i < PAGES_PER_SECTION; i++) {
-               unsigned long pfn = phys_start_pfn + i;
-               struct page *page;
-               if (!pfn_valid(pfn))
-                       continue;
-
-               page = pfn_to_page(pfn);
-               set_page_node(page, nid);
-               SetPageReserved(page);
-       }
-
        if (!want_memblock)
                return 0;
 
@@ -908,8 +890,15 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
        int nid;
        int ret;
        struct memory_notify arg;
+       struct memory_block *mem;
+
+       /*
+        * We can't use pfn_to_nid() because nid might be stored in struct page
+        * which is not yet initialized. Instead, we find nid from memory block.
+        */
+       mem = find_memory_block(__pfn_to_section(pfn));
+       nid = mem->nid;
 
-       nid = pfn_to_nid(pfn);
        /* associate pfn range with the zone */
        zone = move_pfn_range(online_type, nid, pfn, nr_pages);
 

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3183eb2..a3e2ba4 100644 (file)
--- 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);
                }
        }
 }

diff --git a/mm/sparse.c b/mm/sparse.c
index 58cab48..62eef26 100644 (file)
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -779,7 +779,13 @@ int __meminit sparse_add_one_section(struct pglist_data *pgdat,
                goto out;
        }
 
-       memset(memmap, 0, sizeof(struct page) * PAGES_PER_SECTION);
+#ifdef CONFIG_DEBUG_VM
+       /*
+        * Poison uninitialized struct pages in order to catch invalid flags
+        * combinations.
+        */
+       memset(memmap, PAGE_POISON_PATTERN, sizeof(struct page) * PAGES_PER_SECTION);
+#endif
 
        section_mark_present(ms);