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    SubjectRe: [RFC][PATCH 2/7] RSS controller core
    On Sun, Mar 11, 2007 at 12:08:16PM +0300, Pavel Emelianov wrote:
    > Herbert Poetzl wrote:
    >> On Tue, Mar 06, 2007 at 02:00:36PM -0800, Andrew Morton wrote:
    >>> On Tue, 06 Mar 2007 17:55:29 +0300
    >>> Pavel Emelianov <> wrote:
    >>>> +struct rss_container {
    >>>> + struct res_counter res;
    >>>> + struct list_head page_list;
    >>>> + struct container_subsys_state css;
    >>>> +};
    >>>> +
    >>>> +struct page_container {
    >>>> + struct page *page;
    >>>> + struct rss_container *cnt;
    >>>> + struct list_head list;
    >>>> +};
    >>> ah. This looks good. I'll find a hunk of time to go through this
    >>> work and through Paul's patches. It'd be good to get both patchsets
    >>> lined up in -mm within a couple of weeks. But..
    >> doesn't look so good for me, mainly becaus of the
    >> additional per page data and per page processing
    >> on 4GB memory, with 100 guests, 50% shared for each
    >> guest, this basically means ~1mio pages, 500k shared
    >> and 1500k x sizeof(page_container) entries, which
    >> roughly boils down to ~25MB of wasted memory ...
    >> increase the amount of shared pages and it starts
    >> getting worse, but maybe I'm missing something here
    > You are. Each page has only one page_container associated
    > with it despite the number of containers it is shared
    > between.
    >>> We need to decide whether we want to do per-container memory
    >>> limitation via these data structures, or whether we do it via
    >>> a physical scan of some software zone, possibly based on Mel's
    >>> patches.
    >> why not do simple page accounting (as done currently
    >> in Linux) and use that for the limits, without
    >> keeping the reference from container to page?
    > As I've already answered in my previous letter simple
    > limiting w/o per-container reclamation and per-container
    > oom killer isn't a good memory management. It doesn't allow
    > to handle resource shortage gracefully.

    per container OOM killer does not require any container
    page reference, you know _what_ tasks belong to the
    container, and you know their _badness_ from the normal
    OOM calculations, so doing them for a container is really
    straight forward without having any page 'tagging'

    for the reclamation part, please elaborate how that will
    differ in a (shared memory) guest from what the kernel
    currently does ...


    > This patchset provides more grace way to handle this, but
    > full memory management includes accounting of VMA-length
    > as well (returning ENOMEM from system call) but we've decided
    > to start with RSS.
    >> best,
    >> Herbert
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