Re: [LTP] [RFC v13][PATCH 00/14] Kernel based checkpoint/restart

[Subrata M. <su...@li...>]

Serge,

Did i talk to you regarding these tests in our OLS 2008 meeting ? I do
not remember exactly, but, when i saw this posting, i thought may be
there was some conversation.

Regards--
Subrata

On Mon, 2009-03-16 at 17:56 +0530, Subrata Modak wrote:
> Hi Oren,
> 
> On Tue, Jan 27, 2009 at 10:37 PM, Oren Laadan <or...@cs...>
> wrote:
>         Checkpoint-restart (c/r): a couple of fixes in preparation for
>         64bit
>         architectures, and a couple of fixes for bugss (comments from
>         Serge
>         Hallyn, Sudakvev Bhattiprolu and Nathan Lynch). Updated and
>         tested
>         against v2.6.28.
> 
> Can you kindly share those test cases/code with us ?
> 
> Regards--
> Subrata
> 
> 
>         
>         
>         Aiming for -mm.
>         
>         The git tree tracking v13, branch 'ckpt-v13' (and older
>         versions):
>                git://git.ncl.cs.columbia.edu/pub/git/linux-cr.git
>         
>         Restarting multiple processes requires 'mktree' userspace
>         tool:
>                git://git.ncl.cs.columbia.edu/pub/git/user-cr.git
>         
>         Oren.
>         
>         
>         --
>         Why do we want it?  It allows containers to be moved between
>         physical
>         machines' kernels in the same way that VMWare can move VMs
>         between
>         physical machines' hypervisors.  There are currently at least
>         two
>         out-of-tree implementations of this in the commercial world
>         (IBM's
>         Metacluster and Parallels' OpenVZ/Virtuozzo) and several in
>         the academic
>         world like Zap.
>         
>         Why do we need it in mainline now?  Because we already have
>         plenty of
>         out-of-tree ones, and  want to know what an in-tree one will
>         be like.   :)
>         What *I* want right now is the extra review and scrutiny that
>         comes with
>         a mainline submission to make sure we're not going in a
>         direction
>         contrary to the community.
>         
>         This only supports pretty simple apps.  But, I trust Ingo when
>         he says:
>         >> > > Generally, if something works for simple apps already
>         (in a robust,
>         >> > > compatible and supportable way) and users find it "very
>         cool", then
>         >> > > support for more complex apps is not far in the
>         future.  but if you
>         >> > > want to support more complex apps straight away, it
>         takes forever and
>         >> > > gets ugly.
>         
>         We're *certainly* going to be changing the ABI (which is the
>         format of
>         the checkpoint).  I'd like to follow the model that we used
>         for
>         ext4-dev, which is to make it very clear that this is a
>         development-only
>         feature for now.  Perhaps we do that by making the interface
>         only
>         available through debugfs or something similar for now.  Or,
>         reserving
>         the syscall numbers but require some runtime switch to be
>         thrown before
>         they can be used.  I'm open to suggestions here.
>         --
>         
>         --
>         Todo:
>         - Add support for x86-64 and improve ABI
>         - Refine or change syscall interface
>         - Handle multiple namespaces in a container (e.g. save the
>         filesystem
>          namespaces state with the file descriptors)
>         - Security (without CAPS_SYS_ADMIN files restore may fail)
>         
>         Changelog:
>         
>         [2008-Dec-17] v12:
>          - Fix re-alloc/reset of pgarr chain to correctly reuse
>         buffers
>            (empty pgarr are saves in a separate pool chain)
>          - Add a couple of missed calls to cr_hbuf_put()
>          - cr_kwrite/cr_kread() again use vfs_read(), vfs_write()
>         (safer)
>          - Split cr_write/cr_read() to two parts: _cr_write/read()
>         helper
>          - Befriend with sparse: explicit conversion to 'void __user
>         *'
>          - Redrefine 'pr_fmt' ind replace cr_debug() with pr_debug()
>         
>         [2008-Dec-05] v11:
>          - Use contents of 'init->fs->root' instead of pointing to it
>          - Ignore symlinks (there is no such thing as an open symlink)
>          - cr_scan_fds() retries from scratch if it hits size limits
>          - Add missing test for VM_MAYSHARE when dumping memory
>          - Improve documentation about: behavior when tasks aren't
>         fronen,
>            life span of the object hash, references to objects in the
>         hash
>         
>         [2008-Nov-26] v10:
>          - Grab vfs root of container init, rather than current
>         process
>          - Acquire dcache_lock around call to __d_path() in
>         cr_fill_name()
>          - Force end-of-string in cr_read_string() (fix possible DoS)
>          - Introduce cr_write_buffer(), cr_read_buffer() and
>         cr_read_buf_type()
>         
>         [2008-Nov-10] v9:
>          - Support multiple processes c/r
>          - Extend checkpoint header with archtiecture dependent header
>          - Misc bug fixes (see individual changelogs)
>          - Rebase to v2.6.28-rc3.
>         
>         [2008-Oct-29] v8:
>          - Support "external" checkpoint
>          - Include Dave Hansen's 'deny-checkpoint' patch
>          - Split docs in Documentation/checkpoint/..., and improve
>         contents
>         
>         [2008-Oct-17] v7:
>          - Fix save/restore state of FPU
>          - Fix argument given to kunmap_atomic() in memory
>         dump/restore
>         
>         [2008-Oct-07] v6:
>          - Balance all calls to cr_hbuf_get() with matching
>         cr_hbuf_put()
>            (even though it's not really needed)
>          - Add assumptions and what's-missing to documentation
>          - Misc fixes and cleanups
>         
>         [2008-Sep-11] v5:
>          - Config is now 'def_bool n' by default
>          - Improve memory dump/restore code (following Dave Hansen's
>         comments)
>          - Change dump format (and code) to allow chunks of <vaddrs,
>         pages>
>            instead of one long list of each
>          - Fix use of follow_page() to avoid faulting in non-present
>         pages
>          - Memory restore now maps user pages explicitly to copy data
>         into them,
>            instead of reading directly to user space; got rid of
>         mprotect_fixup()
>          - Remove preempt_disable() when restoring debug registers
>          - Rename headers files s/ckpt/checkpoint/
>          - Fix misc bugs in files dump/restore
>          - Fixes and cleanups on some error paths
>          - Fix misc coding style
>         
>         [2008-Sep-09] v4:
>          - Various fixes and clean-ups
>          - Fix calculation of hash table size
>          - Fix header structure alignment
>          - Use stand list_... for cr_pgarr
>         
>         [2008-Aug-29] v3:
>          - Various fixes and clean-ups
>          - Use standard hlist_... for hash table
>          - Better use of standard kmalloc/kfree
>         
>         [2008-Aug-20] v2:
>          - Added Dump and restore of open files (regular and
>         directories)
>          - Added basic handling of shared objects, and improve
>         handling of
>            'parent tag' concept
>          - Added documentation
>          - Improved ABI, 64bit padding for image data
>          - Improved locking when saving/restoring memory
>          - Added UTS information to header (release, version, machine)
>          - Cleanup extraction of filename from a file pointer
>          - Refactor to allow easier reviewing
>          - Remove requirement for CAPS_SYS_ADMIN until we come up with
>         a
>            security policy (this means that file restore may fail)
>          - Other cleanup and response to comments for v1
>         
>         [2008-Jul-29] v1:
>          - Initial version: support a single task with address space
>         of only
>            private anonymous or file-mapped VMAs; syscalls ignore
>         pid/crid
>            argument and act on current process.
>         
>         --
>         At the containers mini-conference before OLS, the consensus
>         among
>         all the stakeholders was that doing checkpoint/restart in the
>         kernel
>         as much as possible was the best approach.  With this
>         approach, the
>         kernel will export a relatively opaque 'blob' of data to
>         userspace
>         which can then be handed to the new kernel at restore time.
>         
>         This is different than what had been proposed before, which
>         was
>         that a userspace application would be responsible for
>         collecting
>         all of this data.  We were also planning on adding lots of
>         new,
>         little kernel interfaces for all of the things that needed
>         checkpointing.  This unites those into a single, grand
>         interface.
>         
>         The 'blob' will contain copies of select portions of kernel
>         structures such as vmas and mm_structs.  It will also contain
>         copies of the actual memory that the process uses.  Any
>         changes
>         in this blob's format between kernel revisions can be handled
>         by
>         an in-userspace conversion program.
>         
>         This is a similar approach to virtually all of the commercial
>         checkpoint/restart products out there, as well as the research
>         project Zap.
>         
>         These patches basically serialize internel kernel state and
>         write
>         it out to a file descriptor.  The checkpoint and restore are
>         done
>         with two new system calls: sys_checkpoint and sys_restart.
>         
>         In this incarnation, they can only work checkpoint and restore
>         a
>         single task. The task's address space may consist of only
>         private,
>         simple vma's - anonymous or file-mapped. The open files may
>         consist
>         of only simple files and directories.
>         --
>         
>         --
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> 
> 
> 
> -- 
> Regards & Thanks--
> Subrata
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