From: Pavel Tatashin <pavel.tatashin@xxxxxxxxxxxxx> Subject: 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@xxxxxxxxx Signed-off-by: Pavel Tatashin <pavel.tatashin@xxxxxxxxxxxxx> Signed-off-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx> Reviewed-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx> Acked-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 46 ++++++++++++++++++++++++++-------------------- 1 file changed, 26 insertions(+), 20 deletions(-) --- a/mm/page_alloc.c~mm-return-zero_resv_unavail-optimization +++ a/mm/page_alloc.c @@ -6511,6 +6511,29 @@ void __init free_area_init_node(int nid, } #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 @@ -6526,7 +6549,6 @@ void __init free_area_init_node(int nid, void __init zero_resv_unavail(void) { phys_addr_t start, end; - unsigned long pfn; u64 i, pgcnt; phys_addr_t next = 0; @@ -6536,34 +6558,18 @@ 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 */ _
