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Andrea Arcangeli
a458b76a41
has_pinned 32bit can be packed in the MMF_HAS_PINNED bit as a noop cleanup. Any atomic_inc/dec to the mm cacheline shared by all threads in pin-fast would reintroduce a loss of SMP scalability to pin-fast, so there's no future potential usefulness to keep an atomic in the mm for this. set_bit(MMF_HAS_PINNED) will be theoretically a bit slower than WRITE_ONCE (atomic_set is equivalent to WRITE_ONCE), but the set_bit (just like atomic_set after this commit) has to be still issued only once per "mm", so the difference between the two will be lost in the noise. will-it-scale "mmap2" shows no change in performance with enterprise config as expected. will-it-scale "pin_fast" retains the > 4000% SMP scalability performance improvement against upstream as expected. This is a noop as far as overall performance and SMP scalability are concerned. [[email protected]: pack has_pinned in MMF_HAS_PINNED] Link: https://lkml.kernel.org/r/YJqWESqyxa8OZA+2@t490s [[email protected]: coding style fixes] [[email protected]: fix build for task_mmu.c, introduce mm_set_has_pinned_flag, fix comments] Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Andrea Arcangeli <[email protected]> Signed-off-by: Peter Xu <[email protected]> Reviewed-by: John Hubbard <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Jan Kara <[email protected]> Cc: Jann Horn <[email protected]> Cc: Jason Gunthorpe <[email protected]> Cc: Kirill Shutemov <[email protected]> Cc: Kirill Tkhai <[email protected]> Cc: Matthew Wilcox <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Oleg Nesterov <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>