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    SubjectRe: [PATCH v9 0/8] stg mail -e --version=v9 \
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    On 11.09.19 15:51, Michal Hocko wrote:
    > On Wed 11-09-19 15:20:02, Michal Hocko wrote:
    > [...]
    >>> 4. Continuously report, not the "one time report everything" approach.
    >>
    >> So you mean the allocator reporting this rather than an external code to
    >> poll right? I do not know, how much this is nice to have than must have?
    >
    > Another idea that I haven't really thought through so it might turned
    > out to be completely bogus but let's try anyway. Your "report everything"
    > just made me look and realize that free_pages_prepare already performs
    > stuff that actually does something similar yet unrelated.
    >
    > We do report to special page poisoning, zeroying or
    > CONFIG_DEBUG_PAGEALLOC to unmap the address from the kernel address
    > space. This sounds like something fitting your model no?
    >

    AFAIKS, the poisoning/unmapping is done whenever a page is freed. I
    don't quite see yet how that would help to remember if a page was
    already reported. After reporting the page we would have to switch some
    state (Nitesh: bitmap bit, Alexander: page flag) to identify that.

    Of course, we could map the page and treat that as "the state" when we
    reported it, but I am not sure that's such a good idea :)

    As always, I might be very wrong ...

    --

    Thanks,

    David / dhildenb

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