• Johannes Weiner's avatar
    mm: thrash detection-based file cache sizing · a528910e
    Johannes Weiner authored
    The VM maintains cached filesystem pages on two types of lists.  One
    list holds the pages recently faulted into the cache, the other list
    holds pages that have been referenced repeatedly on that first list.
    The idea is to prefer reclaiming young pages over those that have shown
    to benefit from caching in the past.  We call the recently usedbut
    ultimately was not significantly better than a FIFO policy and still
    thrashed cache based on eviction speed, rather than actual demand for
    This patch solves one half of the problem by decoupling the ability to
    detect working set changes from the inactive list size.  By maintaining
    a history of recently evicted file pages it can detect frequently used
    pages with an arbitrarily small inactive list size, and subsequently
    apply pressure on the active list based on actual demand for cache, not
    just overall eviction speed.
    Every zone maintains a counter that tracks inactive list aging speed.
    When a page is evicted, a snapshot of this counter is stored in the
    now-empty page cache radix tree slot.  On refault, the minimum access
    distance of the page can be assessed, to evaluate whether the page
    should be part of the active list or not.
    This fixes the VM's blindness towards working set changes in excess of
    the inactive list.  And it's the foundation to further improve the
    protection ability and reduce the minimum inactive list size of 50%.
    Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Reviewed-by: default avatarRik van Riel <riel@redhat.com>
    Reviewed-by: default avatarMinchan Kim <minchan@kernel.org>
    Reviewed-by: default avatarBob Liu <bob.liu@oracle.com>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Christoph Hellwig <hch@infradead.org>
    Cc: Dave Chinner <david@fromorbit.com>
    Cc: Greg Thelen <gthelen@google.com>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Jan Kara <jack@suse.cz>
    Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Cc: Luigi Semenzato <semenzato@google.com>
    Cc: Mel Gorman <mgorman@suse.de>
    Cc: Metin Doslu <metin@citusdata.com>
    Cc: Michel Lespinasse <walken@google.com>
    Cc: Ozgun Erdogan <ozgun@citusdata.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Roman Gushchin <klamm@yandex-team.ru>
    Cc: Ryan Mallon <rmallon@gmail.com>
    Cc: Tejun Heo <tj@kernel.org>
    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>
Makefile 2.09 KB