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    DateMon, 12 Mar 2007 20:19:13 +0300
    FromPavel Emelianov <>
    SubjectRe: [RFC][PATCH 3/7] Data structures changes for RSS accounting
    Dave Hansen wrote:
    > On Mon, 2007-03-12 at 19:16 +0300, Kirill Korotaev wrote:
    >> now VE2 maps the same page. You can't determine whether this page is mapped
    >> to this container or another one w/o page->container pointer. 
    > 
    > Hi Kirill,
    > 
    > I thought we can always get from the page to the VMA.  rmap provides
    > this to us via page->mapping and the 'struct address_space' or anon_vma.
    > Do we agree on that?
    
    Not completely. When page is unmapped from the *very last*
    user its *first* toucher may already be dead. So we'll never
    find out who it was.
    
    > We can also get from the vma to the mm very easily, via vma->vm_mm,
    > right?
    > 
    > We can also get from a task to the container quite easily.  
    > 
    > So, the only question becomes whether there is a 1:1 relationship
    > between mm_structs and containers.  Does each mm_struct belong to one
    
    No. The question is "how to get a container that touched the
    page first" which is the same as "how to find mm_struct which
    touched the page first". Obviously there's no answer on this
    question unless we hold some direct page->container reference.
    This may be a hash, a direct on-page pointer, or mirrored
    array of pointers.
    
    > and only one container?  Basically, can a threaded process have
    > different threads in different containers?
    > 
    > It seems that we could bridge the gap pretty easily by either assigning
    > each mm_struct to a container directly, or putting some kind of
    > task-to-mm lookup.  Perhaps just a list like
    > mm->tasks_using_this_mm_list.
    
    This could work for reclamation: we scan through all the
    mm_struct-s within the container and shrink its' pages, but
    we can't make LRU this way.
    
    > Not rocket science, right?
    > 
    > -- Dave
    > 
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