Re: RFC: Self-snapshotting in Linux - Kernel

This is a discussion on Re: RFC: Self-snapshotting in Linux - Kernel ; Ben Nizette wrote: > On Wed, 2008-04-16 at 16:44 +0800, Peter Teoh wrote: > > Essentially, to reiterate the key idea: able to snapshot the current > > kernel+userspace permanent.....restore from another snapshot....and > > then switch back again if ...

+ Reply to Thread
Results 1 to 7 of 7

Thread: Re: RFC: Self-snapshotting in Linux

  1. Re: RFC: Self-snapshotting in Linux

    Ben Nizette wrote:
    > On Wed, 2008-04-16 at 16:44 +0800, Peter Teoh wrote:
    > > Essentially, to reiterate the key idea: able to snapshot the current
    > > kernel+userspace permanent.....restore from another snapshot....and
    > > then switch back again if needed etc.....will the implementation be
    > > difficult...if not impossible????
    > >

    >
    > As I see it the main thing is that VMWare doesn't have to worry about
    > trying to put hardware in to (and pull out of) low power modes. VMWare
    > hardware is never left in an undefined state by poorly written drivers
    > etc.
    >
    > I think hibernation is about what you want; snapshotting as you describe
    > it should fall down for about the same reasons


    I guess there is the hardware / drivers issue. I would like to claim
    I've found hibernation to be reliable but unfortunately that's not
    100% true. As you say, that's inherent to snapshotting on
    unvirtualised hardware - calling it snapshotting instead of
    hibernation wouldn't change anything.

    I think VMware's real advantages are more about management and
    convenience.
    1) Disk virtualisation. It's much more convenient to create a VMware
    image than a new linux partition. Linux will let you use disk images
    on a filesystem using the loopback driver, but that tends not to be
    well supported by installers. wubi[1] is the obvious counterexample
    here.
    2) Linux hibernation does the in-memory snapshot OK, but the
    *filesystem* obviouslly isn't a part of that snapshot. In some
    unfortunate circumstances, you can end up resuming a memory image
    which is not consistent with the filesystem and corrupting it.
    IMHO filesystems need to include a "last modified" timestamp and check
    it on resume.

    [1] http://wubi-installer.org/
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

  2. Re: RFC: Self-snapshotting in Linux

    > Ben Nizette wrote:
    > > On Wed, 2008-04-16 at 16:44 +0800, Peter Teoh wrote:
    > > > Essentially, to reiterate the key idea: able to snapshot the current
    > > > kernel+userspace permanent.....restore from another snapshot....and
    > > > then switch back again if needed etc.....will the implementation be
    > > > difficult...if not impossible????
    > > >

    > >
    > > As I see it the main thing is that VMWare doesn't have to worry about
    > > trying to put hardware in to (and pull out of) low power modes. VMWare
    > > hardware is never left in an undefined state by poorly written drivers
    > > etc.
    > >
    > > I think hibernation is about what you want; snapshotting as you describe
    > > it should fall down for about the same reasons

    >
    > I guess there is the hardware / drivers issue. I would like to claim
    > I've found hibernation to be reliable but unfortunately that's not
    > 100% true.


    So debug it, it is open source after all. Or at least file a bugs.

    Pavel

    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pav...rses/blog.html
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

  3. Re: RFC: Self-snapshotting in Linux

    Pavel Machek wrote:
    >> I guess there is the hardware / drivers issue. I would like to claim
    >> I've found hibernation to be reliable but unfortunately that's not
    >> 100% true.
    >>

    > So debug it, it is open source after all. Or at least file a bugs.
    >

    I definitely want to debug it; I love hibernating. It's a regression
    and it'll affect my distro kernel once I upgrade to Ubuntu Hardy.

    "Backtraces during
    hibernate / resume".

    I posted the backtraces but nobody could tell me what they were - they
    don't actually say whether they're OOPs or BUGs etc. They might be
    softlockups - some times I got softlockup warnings, though thats not in
    the log I posted.

    The backtraces have been harder to reproduce across different versions /
    configs, but there's definitely an issue where it hangs every time after
    it successfully suspends. It then tends to lock up about a minute after
    resuming.

    I'm confused about some details (exactly which versions / configs
    produced which symptoms). I don't have the machine right now, but I'll
    get back to it some time soon. I think I managed to get a pair of
    broken and non-broken kernels to work on, and it seems to be a
    regression going from 2.6.22 to 2.6.23.

    Any help in clearing up my confusion would be appreciated. Is it worth
    trying to narrow down exactly where the hang happens between writing the
    hibernation image and shutting down? If so how? I suspect that's going
    to be easier than bisecting it.

    Alan
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

  4. Re: RFC: Self-snapshotting in Linux

    Hi.

    On Wed, 2008-04-16 at 03:27 -0700, Alan Jenkins wrote:
    > I guess there is the hardware / drivers issue. I would like to claim
    > I've found hibernation to be reliable but unfortunately that's not
    > 100% true. As you say, that's inherent to snapshotting on
    > unvirtualised hardware - calling it snapshotting instead of
    > hibernation wouldn't change anything.


    On a particular set of hardware, it should be possible to make it 100%
    reliable. If you've found bugs, please report them. We can only fix
    issues if we know they exist.

    Regards,

    Nigel

    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

  5. Re: RFC: Self-snapshotting in Linux

    Nigel Cunningham wrote:
    > Hi.
    >
    > On Wed, 2008-04-16 at 03:27 -0700, Alan Jenkins wrote:
    >
    >> I guess there is the hardware / drivers issue. I would like to claim
    >> I've found hibernation to be reliable but unfortunately that's not
    >> 100% true. As you say, that's inherent to snapshotting on
    >> unvirtualised hardware - calling it snapshotting instead of
    >> hibernation wouldn't change anything.
    >>

    >
    > On a particular set of hardware, it should be possible to make it 100%
    > reliable. If you've found bugs, please report them. We can only fix
    > issues if we know they exist.
    >

    Thanks!

    I already replied to Pavels similar comment - I had posted on Bugzilla.
    I guess it missed the right people because it started off in the wrong
    category. (The first symptom I reported was my 2.13Ghz cpu running at
    1Ghz after a sucessful hibernation cycle). At Rafaels request, I shall
    be retesting with the latest 2.6.25-rc kernel on Saturday. I look
    forward to getting it fixed - I know it should be possible because it's
    a regression.

    Alan
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

  6. Re: RFC: Self-snapshotting in Linux

    On Wed 2008-04-16 14:50:46, Alan Jenkins wrote:
    > Pavel Machek wrote:
    >>> I guess there is the hardware / drivers issue. I would like to claim
    >>> I've found hibernation to be reliable but unfortunately that's not
    >>> 100% true.
    >>>

    >> So debug it, it is open source after all. Or at least file a bugs.
    >>

    > I definitely want to debug it; I love hibernating. It's a regression and
    > it'll affect my distro kernel once I upgrade to Ubuntu Hardy.
    >
    > "Backtraces during
    > hibernate / resume".
    >
    > I posted the backtraces but nobody could tell me what they were - they
    > don't actually say whether they're OOPs or BUGs etc. They might be
    > softlockups - some times I got softlockup warnings, though thats not in the
    > log I posted.


    Not sure what that is, I never seen that before.

    Can you try vanilla 2.6.25-rc9 or something?

    > I'm confused about some details (exactly which versions / configs produced
    > which symptoms). I don't have the machine right now, but I'll get back to
    > it some time soon. I think I managed to get a pair of broken and
    > non-broken kernels to work on, and it seems to be a regression going from
    > 2.6.22 to 2.6.23.


    If you can do a git bisect between those two, we could probably fix it
    very quickly.

    > Any help in clearing up my confusion would be appreciated. Is it worth
    > trying to narrow down exactly where the hang happens between writing the
    > hibernation image and shutting down? If so how? I suspect that's going to
    > be easier than bisecting it.


    Adding printks?
    Pavel
    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pav...rses/blog.html
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

  7. Re: RFC: Self-snapshotting in Linux

    Pavel Machek wrote:
    > On Wed 2008-04-16 14:50:46, Alan Jenkins wrote:
    >
    >> Pavel Machek wrote:
    >>
    >>>> I guess there is the hardware / drivers issue. I would like to claim
    >>>> I've found hibernation to be reliable but unfortunately that's not
    >>>> 100% true.
    >>>>
    >>>>
    >>> So debug it, it is open source after all. Or at least file a bugs.
    >>>
    >>>

    >> I definitely want to debug it; I love hibernating. It's a regression and
    >> it'll affect my distro kernel once I upgrade to Ubuntu Hardy.
    >>
    >> "Backtraces during
    >> hibernate / resume".
    >>
    >> I posted the backtraces but nobody could tell me what they were - they
    >> don't actually say whether they're OOPs or BUGs etc. They might be
    >> softlockups - some times I got softlockup warnings, though thats not in the
    >> log I posted.
    >>

    >
    > Not sure what that is, I never seen that before.
    >
    > Can you try vanilla 2.6.25-rc9 or something?
    >

    I've just retested with 2.6.25. I reproduced the hang that happens
    after (otherwise successful) hibernation. After a second hibernation &
    resume I reproduced the mysterious call-traces.

    I posted this information, a full system log (including 2 hibernation
    cycles and the calltraces), and the kernel config to the bugzilla entry.

    This was in response to Rafael's request on the bugzilla. So I expect
    someone will look at it anyway, but I thought I should copy you on this.

    Thanks,

    Alan
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

+ Reply to Thread