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Commit d0dc12e8 authored by Pavel Tatashin's avatar Pavel Tatashin Committed by Linus Torvalds
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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: default avatarPavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: default avatarIngo 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fc44f7f9

drivers/base/node.c

+2 −0
Original line number Diff line number Diff line
@@ -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;

include/linux/memory.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

mm/memory_hotplug.c

+8 −19
Original line number Diff line number Diff line
@@ -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);

mm/page_alloc.c

+10 −18
Original line number Diff line number Diff line
@@ -1143,9 +1143,8 @@ 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);

	set_page_links(page, zone, nid, pfn);

	init_page_count(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 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, 
		 * 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);

		}

	}

}

mm/sparse.c

+7 −1
Original line number Diff line number Diff line
@@ -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);