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Commit ec393a0f authored by Pavel Tatashin's avatar Pavel Tatashin Committed by Linus Torvalds
Browse files

mm: return zero_resv_unavail optimization 

When checking for valid pfns in zero_resv_unavail(), it is not necessary
to verify that pfns within pageblock_nr_pages ranges are valid, only the
first one needs to be checked.  This is because memory for pages are
allocated in contiguous chunks that contain pageblock_nr_pages struct
pages.

Link: http://lkml.kernel.org/r/20181002143821.5112-3-msys.mizuma@gmail.com


Signed-off-by: default avatarPavel Tatashin <pavel.tatashin@microsoft.com>
Signed-off-by: default avatarMasayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Reviewed-by: default avatarMasayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Acked-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: default avatarOscar Salvador <osalvador@suse.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 907ec5fc

mm/page_alloc.c

+26 −20
Original line number Diff line number Diff line
@@ -6509,6 +6509,29 @@ void __init free_area_init_node(int nid, unsigned long *zones_size, 
}



#if defined(CONFIG_HAVE_MEMBLOCK) && !defined(CONFIG_FLAT_NODE_MEM_MAP)



/*

 * Zero all valid struct pages in range [spfn, epfn), return number of struct

 * pages zeroed

 */

static u64 zero_pfn_range(unsigned long spfn, unsigned long epfn)

{

	unsigned long pfn;

	u64 pgcnt = 0;



	for (pfn = spfn; pfn < epfn; pfn++) {

		if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) {

			pfn = ALIGN_DOWN(pfn, pageblock_nr_pages)

				+ pageblock_nr_pages - 1;

			continue;

		}

		mm_zero_struct_page(pfn_to_page(pfn));

		pgcnt++;

	}



	return pgcnt;

}



/*

 * Only struct pages that are backed by physical memory are zeroed and

 * initialized by going through __init_single_page(). But, there are some
@@ -6524,7 +6547,6 @@ void __init free_area_init_node(int nid, unsigned long *zones_size, 
void __init zero_resv_unavail(void)

{

	phys_addr_t start, end;

	unsigned long pfn;

	u64 i, pgcnt;

	phys_addr_t next = 0;
@@ -6534,34 +6556,18 @@ void __init zero_resv_unavail(void) 
	pgcnt = 0;

	for_each_mem_range(i, &memblock.memory, NULL,

			NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end, NULL) {

		if (next < start) {

			for (pfn = PFN_DOWN(next); pfn < PFN_UP(start); pfn++) {

				if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages)))

					continue;

				mm_zero_struct_page(pfn_to_page(pfn));

				pgcnt++;

			}

		}

		if (next < start)

			pgcnt += zero_pfn_range(PFN_DOWN(next), PFN_UP(start));

		next = end;

	}

	for (pfn = PFN_DOWN(next); pfn < max_pfn; pfn++) {

		if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages)))

			continue;

		mm_zero_struct_page(pfn_to_page(pfn));

		pgcnt++;

	}



	pgcnt += zero_pfn_range(PFN_DOWN(next), max_pfn);



	/*

	 * Struct pages that do not have backing memory. This could be because

	 * firmware is using some of this memory, or for some other reasons.

	 * Once memblock is changed so such behaviour is not allowed: i.e.

	 * list of "reserved" memory must be a subset of list of "memory", then

	 * this code can be removed.

	 */

	if (pgcnt)

		pr_info("Zeroed struct page in unavailable ranges: %lld pages", pgcnt);



}

#endif /* CONFIG_HAVE_MEMBLOCK && !CONFIG_FLAT_NODE_MEM_MAP */