• Mel Gorman's avatar
    mm, truncate: do not check mapping for every page being truncated · c7df8ad2
    Mel Gorman authored
    During truncation, the mapping has already been checked for shmem and
    dax so it's known that workingset_update_node is required.
    
    This patch avoids the checks on mapping for each page being truncated.
    In all other cases, a lookup helper is used to determine if
    workingset_update_node() needs to be called.  The one danger is that the
    API is slightly harder to use as calling workingset_update_node directly
    without checking for dax or shmem mappings could lead to surprises.
    However, the API rarely needs to be used and hopefully the comment is
    enough to give people the hint.
    
    sparsetruncate (tiny)
                                  4.14.0-rc4             4.14.0-rc4
                                 oneirq-v1r1        pickhelper-v1r1
    Min          Time      141.00 (   0.00%)      140.00 (   0.71%)
    1st-qrtle    Time      142.00 (   0.00%)      141.00 (   0.70%)
    2nd-qrtle    Time      142.00 (   0.00%)      142.00 (   0.00%)
    3rd-qrtle    Time      143.00 (   0.00%)      143.00 (   0.00%)
    Max-90%      Time      144.00 (   0.00%)      144.00 (   0.00%)
    Max-95%      Time      147.00 (   0.00%)      145.00 (   1.36%)
    Max-99%      Time      195.00 (   0.00%)      191.00 (   2.05%)
    Max          Time      230.00 (   0.00%)      205.00 (  10.87%)
    Amean        Time      144.37 (   0.00%)      143.82 (   0.38%)
    Stddev       Time       10.44 (   0.00%)        9.00 (  13.74%)
    Coeff        Time        7.23 (   0.00%)        6.26 (  13.41%)
    Best99%Amean Time      143.72 (   0.00%)      143.34 (   0.26%)
    Best95%Amean Time      142.37 (   0.00%)      142.00 (   0.26%)
    Best90%Amean Time      142.19 (   0.00%)      141.85 (   0.24%)
    Best75%Amean Time      141.92 (   0.00%)      141.58 (   0.24%)
    Best50%Amean Time      141.69 (   0.00%)      141.31 (   0.27%)
    Best25%Amean Time      141.38 (   0.00%)      140.97 (   0.29%)
    
    As you'd expect, the gain is marginal but it can be detected.  The
    differences in bonnie are all within the noise which is not surprising
    given the impact on the microbenchmark.
    
    radix_tree_update_node_t is a callback for some radix operations that
    optionally passes in a private field.  The only user of the callback is
    workingset_update_node and as it no longer requires a mapping, the
    private field is removed.
    
    Link: http://lkml.kernel.org/r/20171018075952.10627-3-mgorman@techsingularity.netSigned-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
    Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Reviewed-by: default avatarJan Kara <jack@suse.cz>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: Dave Chinner <david@fromorbit.com>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    c7df8ad2