• Mel Gorman's avatar
    mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep... · d0164adc
    Mel Gorman authored
    mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd
    
    __GFP_WAIT has been used to identify atomic context in callers that hold
    spinlocks or are in interrupts.  They are expected to be high priority and
    have access one of two watermarks lower than "min" which can be referred
    to as the "atomic reserve".  __GFP_HIGH users get access to the first
    lower watermark and can be called the "high priority reserve".
    
    Over time, callers had a requirement to not block when fallback options
    were available.  Some have abused __GFP_WAIT leading to a situation where
    an optimisitic allocation with a fallback option can access atomic
    reserves.
    
    This patch uses __GFP_ATOMIC to identify callers that are truely atomic,
    cannot sleep and have no alternative.  High priority users continue to use
    __GFP_HIGH.  __GFP_DIRECT_RECLAIM identifies callers that can sleep and
    are willing to enter direct reclaim.  __GFP_KSWAPD_RECLAIM to identify
    callers that want to wake kswapd for backgrou...
    d0164adc