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    SubjectRe: [RFC v4] UBI: Fastmap support (aka checkpointing)
    On 16.05.2012 13:18, Artem Bityutskiy wrote:
    > On Wed, 2012-05-16 at 14:09 +0300, Artem Bityutskiy wrote:
    >>> The maximum size of a fastmap is limited to UBI_FM_MAX_BLOCKS.
    >>> As I said, in worst case we'd have to scan 192 PEBs, which is a constant.
    >> In this case you cannot use O notation at all because it is just used
    >> when talking about asymptotic things.
    > OK, we are talking about different things. It is fine that you need to
    > scan 192 eraseblocks, this is kind of your journal. And this part may be
    > O(1). But there is another part as well.

    Yeah, seems to.

    > But as I already explained, you have a _table_ on the flash, and this
    > table stores Erase Counter and LEB number for (roughly) each PEB. The
    > more PEBs, the large is the table, linerarly.
    > As I explained, you have to _read_ and _interpret_ each record in this
    > table when attaching. And the more of these records you have, the longer
    > it takes to attach. And this is where you have your O(N).

    Okay, now I understand your point. :)

    > So basically fastmap makes UBI's linerar dependency multiplier a lot
    > smaller, so it is still a great improvement.



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