• David Rientjes's avatar
    oom: avoid oom killer for lowmem allocations · 03668b3c
    David Rientjes authored
    If memory has been depleted in lowmem zones even with the protection
    afforded to it by /proc/sys/vm/lowmem_reserve_ratio, it is unlikely that
    killing current users will help.  The memory is either reclaimable (or
    migratable) already, in which case we should not invoke the oom killer at
    all, or it is pinned by an application for I/O.  Killing such an
    application may leave the hardware in an unspecified state and there is no
    guarantee that it will be able to make a timely exit.
    
    Lowmem allocations are now failed in oom conditions when __GFP_NOFAIL is
    not used so that the task can perhaps recover or try again later.
    
    Previously, the heuristic provided some protection for those tasks with
    CAP_SYS_RAWIO, but this is no longer necessary since we will not be
    killing tasks for the purposes of ISA allocations.
    
    high_zoneidx is gfp_zone(gfp_flags), meaning that ZONE_NORMAL will be the
    default for all allocations that are not __GFP_DMA, __GFP_DMA32,
    __GFP_HIGHMEM, and __GFP_MOVABLE on kernels configured to support those
    flags.  Testing for high_zoneidx being less than ZONE_NORMAL will only
    return true for allocations that have either __GFP_DMA or __GFP_DMA32.
    Acked-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    03668b3c
page_alloc.c 151 KB