From d0dc12e86b3197a14a908d4fe7cb35b73dda82b5 Mon Sep 17 00:00:00 2001 From: Pavel Tatashin Date: Thu, 5 Apr 2018 16:23:00 -0700 Subject: 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 Reviewed-by: Ingo Molnar Cc: Michal Hocko Cc: Baoquan He Cc: Bharata B Rao Cc: Daniel Jordan Cc: Dan Williams Cc: Greg Kroah-Hartman Cc: "H. Peter Anvin" Cc: Kirill A. Shutemov Cc: Mel Gorman Cc: Steven Sistare Cc: Thomas Gleixner Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/sparse.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'mm/sparse.c') diff --git a/mm/sparse.c b/mm/sparse.c index 58cab483e81b..62eef264a7bd 100644 --- 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); -- cgit v1.2.3-59-g8ed1b