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    [PATCH] mm: move_page_tables by extents · 7be7a546
    Hugh Dickins 提交于
    Speeding up mremap's moving of ptes has never been a priority, but the locking
    will get more complicated shortly, and is already too baroque.
    
    Scrap the current one-by-one moving, do an extent at a time: curtailed by end
    of src and dst pmds (have to use PMD_SIZE: the way pmd_addr_end gets elided
    doesn't match this usage), and by latency considerations.
    
    One nice property of the old method is lost: it never allocated a page table
    unless absolutely necessary, so you could free empty page tables by mremapping
    to and fro.  Whereas this way, it allocates a dst table wherever there was a
    src table.  I keep diving in to reinstate the old behaviour, then come out
    preferring not to clutter how it now is.
    Signed-off-by: NHugh Dickins <hugh@veritas.com>
    Signed-off-by: NAndrew Morton <akpm@osdl.org>
    Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
    7be7a546
mremap.c 10.3 KB