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Pavel Tatashin
d0dc12e86b
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. [[email protected]: v5] Link: http://lkml.kernel.org/r/[email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Pavel Tatashin <[email protected]> Reviewed-by: Ingo Molnar <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Baoquan He <[email protected]> Cc: Bharata B Rao <[email protected]> Cc: Daniel Jordan <[email protected]> Cc: Dan Williams <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Kirill A. Shutemov <[email protected]> Cc: Mel Gorman <[email protected]> Cc: Steven Sistare <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Vlastimil Babka <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>