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    [PATCH] htlb forget rss with pt sharing · cace673d
    Chen, Kenneth W 提交于
    Imprecise RSS accounting is an irritating ill effect with pt sharing.  After
    consulted with several VM experts, I have tried various methods to solve that
    problem: (1) iterate through all mm_structs that share the PT and increment
    count; (2) keep RSS count in page table structure and then sum them up at
    reporting time.  None of the above methods yield any satisfactory
    implementation.
    
    Since process RSS accounting is pure information only, I propose we don't
    count them at all for hugetlb page.  rlimit has such field, though there is
    absolutely no enforcement on limiting that resource.  One other method is to
    account all RSS at hugetlb mmap time regardless they are faulted or not.  I
    opt for the simplicity of no accounting at all.
    
    Hugetlb page are special, they are reserved up front in global reservation
    pool and is not reclaimable.  From physical memory resource point of view, it
    is already consumed regardless whether there are users using them.
    
    If the concern is that RSS can be used to control resource allocation, we
    already can specify hugetlb fs size limit and sysadmin can enforce that at
    mount time.  Combined with the two points mentioned above, I fail to see if
    there is anything got affected because of this patch.
    Signed-off-by: NKen Chen <kenneth.w.chen@intel.com>
    Acked-by: NHugh Dickins <hugh@veritas.com>
    Cc: Dave McCracken <dmccr@us.ibm.com>
    Cc: William Lee Irwin III <wli@holomorphy.com>
    Cc: "Luck, Tony" <tony.luck@intel.com>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: David Gibson <david@gibson.dropbear.id.au>
    Cc: Adam Litke <agl@us.ibm.com>
    Cc: Paul Mundt <lethal@linux-sh.org>
    Cc: "David S. Miller" <davem@davemloft.net>
    Signed-off-by: NAndrew Morton <akpm@osdl.org>
    Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
    cace673d
hugetlb.c 19.3 KB