• Vlastimil Babka's avatar
    mm, slab/slub: introduce kmalloc-reclaimable caches · 1291523f
    Vlastimil Babka authored
    Kmem caches can be created with a SLAB_RECLAIM_ACCOUNT flag, which
    indicates they contain objects which can be reclaimed under memory
    pressure (typically through a shrinker).  This makes the slab pages
    accounted as NR_SLAB_RECLAIMABLE in vmstat, which is reflected also the
    MemAvailable meminfo counter and in overcommit decisions.  The slab pages
    are also allocated with __GFP_RECLAIMABLE, which is good for
    anti-fragmentation through grouping pages by mobility.
    
    The generic kmalloc-X caches are created without this flag, but sometimes
    are used also for objects that can be reclaimed, which due to varying size
    cannot have a dedicated kmem cache with SLAB_RECLAIM_ACCOUNT flag.  A
    prominent example are dcache external names, which prompted the creation
    of a new, manually managed vmstat counter NR_INDIRECTLY_RECLAIMABLE_BYTES
    in commit f1782c9b ("dcache: account external names as indirectly
    reclaimable memory").
    
    To better handle this and any other similar cases, this patch introduces
    SLAB_RECLAIM_ACCOUNT variants of kmalloc caches, named kmalloc-rcl-X.
    They are used whenever the kmalloc() call passes __GFP_RECLAIMABLE among
    gfp flags.  They are added to the kmalloc_caches array as a new type.
    Allocations with both __GFP_DMA and __GFP_RECLAIMABLE will use a dma type
    cache.
    
    This change only applies to SLAB and SLUB, not SLOB.  This is fine, since
    SLOB's target are tiny system and this patch does add some overhead of
    kmem management objects.
    
    Link: http://lkml.kernel.org/r/20180731090649.16028-3-vbabka@suse.czSigned-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
    Acked-by: default avatarMel Gorman <mgorman@techsingularity.net>
    Acked-by: default avatarChristoph Lameter <cl@linux.com>
    Acked-by: default avatarRoman Gushchin <guro@fb.com>
    Cc: David Rientjes <rientjes@google.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    Cc: Laura Abbott <labbott@redhat.com>
    Cc: Matthew Wilcox <willy@infradead.org>
    Cc: Michal Hocko <mhocko@kernel.org>
    Cc: Sumit Semwal <sumit.semwal@linaro.org>
    Cc: Vijayanand Jitta <vjitta@codeaurora.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    1291523f
slab_common.c 37.7 KB