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    SubjectRe: [GIT PULL] mm: frontswap (for 3.2 window)
    On Mon, 31 Oct 2011 09:38:12 -0700 (PDT)
    Dan Magenheimer <> wrote:

    > > From: KAMEZAWA Hiroyuki []
    > > Subject: Re: [GIT PULL] mm: frontswap (for 3.2 window)
    > Hi Kame --
    > Thanks for your reply and for your earlier reviews of frontswap,
    > and my apologies that I accidentally left you off of the Cc list \
    > for the basenote of this git-pull request.
    > > I don't have heavy concerns to the codes itself but this process as bypassing -mm
    > > or linux-next seems ugly.
    > First, frontswap IS in linux-next and it has been since June 3
    > and v11 has been in linux-next since September 23. This
    > is stated in the base git-pull request.

    Ok, I'm sorry. I found frontswap.c in my tree.

    > > Why bypass -mm tree ?
    > >
    > > I think you planned to merge this via -mm tree and, then, posted patches
    > > to linux-mm with CC -mm guys.
    > Hmmm... the mm process is not clear or well-documented.

    not complicated to me.

    post -> akpm's -mm tree -> mainline.

    But your tree seems to be in -mm via linux-next. Hmm, complicated ;(
    I'm sorry I didn't notice frontswap.c was there....

    > > I think you posted 2011/09/16 at the last time, v10. But no further submission
    > > to gather acks/reviews from Mel, Johannes, Andrew, Hugh etc.. and no inclusion
    > > request to -mm or -next. _AND_, IIUC, at v10, the number of posted pathces was 6.
    > > Why now 8 ? Just because it's simple changes ?
    > See Konrad Wilk
    > helped me to reorganize the patches (closer to what you
    > suggested I think), but there were no code changes between
    > v10 and v11, just dividing up the patches differently
    > as Konrad thought there should be more smaller commits.
    > So no code change between v10 and v11 but the number of
    > patches went from 6 to 8.
    > My last line in that post should also make it clear that
    > I thought I was done and ready for the 3.2 window, so there
    > was no evil intent on my part to subvert a process.
    > It would have been nice if someone had told me there
    > were uncompleted steps in the -mm process or, even better,
    > pointed me to a (non-existent?) document where I could see
    > for myself if I was missing steps!
    > So... now what?

    As far as I know, patches for memory management should go through akpm's tree.
    And most of developpers in that area see that tree.
    Now, your tree goes through linux-next. It complicates the problem.

    When a patch goes through -mm tree, its justification is already checked by
    , at least, akpm. And while in -mm tree, other developpers checks it and
    some improvements are done there.

    Now, you tries to push patches via linux-next and your
    justification for patches is checked _now_. That's what happens.
    It's not complicated. I think other linux-next patches are checked
    its justification at pull request.

    So, all your work will be to convice people that this feature is
    necessary and not-intrusive, here.

    From my point of view,

    - I have no concerns with performance cost. But, at the same time,
    I want to see performance improvement numbers.

    - At discussing an fujitsu user support guy (just now), he asked
    'why it's not designed as device driver ?"
    I couldn't answered.

    So, I have small concerns with frontswap.ops ABI design.
    Do we need ABI and other modules should be pluggable ?
    Can frontswap be implemented as something like

    # setup frontswap via device-mapper or some.
    # swapon /dev/frontswap
    It seems required hooks are just before/after read/write swap device.
    other hooks can be implemented in ?


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