• Christoph Lameter's avatar
    [PATCH] Use ZVC for inactive and active counts · c8785385
    Christoph Lameter authored
    The determination of the dirty ratio to determine writeback behavior is
    currently based on the number of total pages on the system.
    
    However, not all pages in the system may be dirtied.  Thus the ratio is always
    too low and can never reach 100%.  The ratio may be particularly skewed if
    large hugepage allocations, slab allocations or device driver buffers make
    large sections of memory not available anymore.  In that case we may get into
    a situation in which f.e.  the background writeback ratio of 40% cannot be
    reached anymore which leads to undesired writeback behavior.
    
    This patchset fixes that issue by determining the ratio based on the actual
    pages that may potentially be dirty.  These are the pages on the active and
    the inactive list plus free pages.
    
    The problem with those counts has so far been that it is expensive to
    calculate these because counts from multiple nodes and multiple zones will
    have to be summed up.  This patchset makes these counters ZVC counters.  This
    means that a current sum per zone, per node and for the whole system is always
    available via global variables and not expensive anymore to calculate.
    
    The patchset results in some other good side effects:
    
    - Removal of the various functions that sum up free, active and inactive
      page counts
    
    - Cleanup of the functions that display information via the proc filesystem.
    
    This patch:
    
    The use of a ZVC for nr_inactive and nr_active allows a simplification of some
    counter operations.  More ZVC functionality is used for sums etc in the
    following patches.
    
    [akpm@osdl.org: UP build fix]
    Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    c8785385
vmscan.c 47.2 KB