• Rik van Riel's avatar
    /proc/meminfo: provide estimated available memory · 34e431b0
    Rik van Riel authored
    
    
    Many load balancing and workload placing programs check /proc/meminfo to
    estimate how much free memory is available.  They generally do this by
    adding up "free" and "cached", which was fine ten years ago, but is
    pretty much guaranteed to be wrong today.
    
    It is wrong because Cached includes memory that is not freeable as page
    cache, for example shared memory segments, tmpfs, and ramfs, and it does
    not include reclaimable slab memory, which can take up a large fraction
    of system memory on mostly idle systems with lots of files.
    
    Currently, the amount of memory that is available for a new workload,
    without pushing the system into swap, can be estimated from MemFree,
    Active(file), Inactive(file), and SReclaimable, as well as the "low"
    watermarks from /proc/zoneinfo.
    
    However, this may change in the future, and user space really should not
    be expected to know kernel internals to come up with an estimate for the
    amount of free memory.
    
    It is more convenient to provide such an estimate in /proc/meminfo.  If
    things change in the future, we only have to change it in one place.
    Signed-off-by: default avatarRik van Riel <riel@redhat.com>
    Reported-by: default avatarErik Mouw <erik.mouw_2@nxp.com>
    Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    34e431b0
proc.txt 79.5 KB