• Aaro Koskinen's avatar
    [ARM] 5450/1: Flush only the needed range when unmapping a VMA · 7fccfc00
    Aaro Koskinen authored
    When unmapping N pages (e.g. shared memory) the amount of TLB flushes
    done can be (N*PAGE_SIZE/ZAP_BLOCK_SIZE)*N although it should be N at
    maximum. With PREEMPT kernel ZAP_BLOCK_SIZE is 8 pages, so there is a
    noticeable performance penalty when unmapping a large VMA and the system
    is spending its time in flush_tlb_range().
    
    The problem is that tlb_end_vma() is always flushing the full VMA
    range. The subrange that needs to be flushed can be calculated by
    tlb_remove_tlb_entry(). This approach was suggested by Hugh Dickins,
    and is also used by other arches.
    
    The speed increase is roughly 3x for 8M mappings and for larger mappings
    even more.
    Signed-off-by: default avatarAaro Koskinen <Aaro.Koskinen@nokia.com>
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    7fccfc00
tlb.h 2.66 KB