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    SubjectRe: Which is simpler? (Was Re: [Suspend2-devel] Re: [ 00/10] [Suspend2] Modules support.)
    Date
    Hi.

    On Monday 20 February 2006 07:29, Pavel Machek wrote:
    > Hi!
    >
    > > > swsusp is also available today, and works better than you think. It is
    > > > slightly slower, but has all the other
    > > > features you listed in 2.6.16-rc3.
    > >
    > > It is a lot slower because it does all it's I/O synchronously, doesn't
    > > compress the image and throws away memory until at least half is
    > > free.
    >
    > uswsusp does compress image (20% speedup, in recent CVS) and do
    > asynchronous I/O.

    Only 20? You must be doing something horribly wrong. Asynchronous I/O shoudl
    get the speed from whatever you're getting without it to the maximum the
    drive can handle. LZF should double the speed again on a CPU that's fast
    enough that the bottleneck is the disk.

    > > > > The only con I see is the complexity of the code, but then again,
    > > > > Nigel
    > > >
    > > > ..but thats a big con.
    > >
    > > It's fud. Hopefully as I post more suspend2 patches to LKML, people will
    > > see that Suspend2 is simpler than what you are planning.
    >
    > For what I'm planning, all the neccessary patches are already in -mm
    > tree. And they are *really* simple. If you can get suspend2 to 1000
    > lines of code (like Rafael did with uswsusp), we can have something to
    > talk about.

    Turn it round the right way. If you can get the functionality of Suspend2
    using userspace only, then we have something to talk about.

    > > > > From a user, and contributor, point of view, I really do not
    > > > > understand why not even trying to push a working implementation into
    > > > > mainline (I know that you cannot just apply the Suspend 2 patches and
    > > > > shipping it,
    > > >
    > > > It is less work to port suspend2's features into userspace than to make
    > > > suspend2 acceptable to mainline. Both will mean big changes, and may
    > > > cause some short-term problems, but it will be less pain than
    > > > maintaining suspend2 forever. Please help with the former...
    > >
    > > That's not true. I've taken time to look at what would be involved in
    > > making suspend2 match the changes you're doing, and I've decided it's
    > > just not worth the effort.
    > >
    > > Let's be clear. uswsusp is not really moving suspend-to-disk to
    > > userspace. What it is doing is leaving everything but some code for
    > > writing the image in kernel space, and implementing ioctls to give a
    > > userspace program the ability to request that other processes be frozen,
    > > the snapshot prepared and so on. Pages in the snapshot are copied to
    > > userspace, possibly compressed or encrypted there in future, then fed
    > > back to kernel space so it can use the swap routines to do the writing.
    > > Very little of substance is being done in userspace. In short, all it's
    > > doing is adding the complexity of
    >
    > Maybe very little of substance is being done in userspace, but all the
    > uglyness can stay there. I no longer need LZF in kernel, special
    > netlink API for progress bar (progress bar naturally lives in
    > userland), no plugin infrastructure needed, etc.

    And you do need?...

    > If you can do suspend2 without putting stuff listed above into kernel,
    > and in acceptable ammount of code... we can see. But you should really
    > put suspend2 code into userspace, and be done with that. Feel free to
    > spam l-k a bit more, but using existing infrastructure in -mm is right
    > way to go, and it is easier, too.

    It is only easier because you're not comparing apples with apples. I have no
    desire to spam LKML with this pointless discussion, so I'm just going to get
    on with submitting patches for review.

    Rgards,

    Nigel

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