[Devel] Re: Linux Checkpoint-Restart - v19

[Jiro SEKIBA]

Hi,
On 2010/03/18, at 5:55, Serge E. Hallyn wrote:

> Quoting Jiro SEKIBA (jir at dependable-os.net):
>> Hi,
>> 
>> Thank you for prompt reply!
>> Sorry that I didn't post to containers at lists.linux-foundation.org.
>> 
>> On 2010/03/16, at 7:55, Oren Laadan wrote:
>> 
>>> Hi,
>>> 
>>> Thanks for taking the time to evaluate c/r. You may want to also
>>> try the latest, which is (as of now) ckpt-v20-rc2.
>> 
>> Yeah, I'll eventually try to keep up with the latest,
>> but I just want to try the one  you think it's stable first anyway.
>> 
>>> In the future, please CC the containers mailing list for issues
>>> related to c/r, at "containers at lists.linux-foundation.org".
>>> 
>>> Jiro SEKIBA wrote:
>>>> Hi,
>>>> I'm trying to evaluate external checkpoint/restart with cr-v19 kernel.
>>>> However, when I restart, I got "Killed" message in stdout.
>>>> Do you have any tips or clue that are not in
>>>> Documentation/checkpoint/usage.txt ?
>>>> I'm using kernel pulled from
>>>> git://git.ncl.cs.columbia.edu/pub/git/linux-cr.git .
>>>> checkout tag named "ckpt-v19". Base distro is ubuntu 9.10.
>>>> I ran self checkpioint/restart sample program in Documentation/checkpint.
>>>> It works as written in usage.txt.
>>>> However, I can not make external checkpint/restart work properly.
>>>> I made a simple test program bellow and create checkpoint externally using
>>>> the program in Documentation/checkpoint/, it looks checkpoint file is
>>>> created properly.
>>>> However, when I ran self_restart < ckpt.image, I got "Killed" message.
>>> 
>>> If you take an external checkpoint, then you need to match it
>>> with an external restart, as opposed to self_restart.
>>> 
>>> Otherwise, restarting with self_restart from a checkpoint that is
>>> not a self-checkpoint can yield unexpected results.
>>> 
>>> Since you don't mention in your post, I don't know if you are using
>>> the tools from user-cr. If not, then you should use 'checkpoint' and
>>> 'restart' tools from there. It is available from:
>>> 	git://git.ncl.cs.columbia.edu/pub/git/user-cr.git
>>> (use the same branch as the one you used to linux-cr).
>>> 
>>> Once you have the tools compiled, and you checkpoint with the
>>> 'checkpoint' utility from there, you can restart with:
>>> 	restart -v < ckpt.image
>>> 
>> 
>> Thank you for the information.
>> Actually I was trying to create checkpoint in Document/checkpints.
>> 
>> Now, I tried with user-cr, compiled binary in the same tag (ckpt-v19).
>> Creating checkpoint  looks OK and restart -v shows it Success.  nice!
>> However, the contents in /tmp/test.out never get further,
>> it remains same as when created checkpoint.
>> 
>> I tried  "./restart -F /cgroup/0 -v --no-pidns < ckpt.image", got Success.
>> cat /cgroup/0/tasks tells that there is a process.
>> ps shows ./test.  So, it looks restarting.
>> 
>> # ps axuww |grep $(cat /cgroup/0/tasks )
>> root      7231  0.1  0.0   1588    64 pts/0    D    16:57   0:00 ./test
>> root      7238  0.0  0.1   2716   660 pts/1    R+   16:57   0:00 grep 7231
>> 
>> under the /proc, one file descriptor opened, and it is /tmp/test.out
>> 
>> #  ls -l /proc/$(cat /cgroup/0/tasks)/fd
>> total 0
>> lrwx------ 1 root root 64 Mar 16 16:58 0 -> /tmp/test.out
>> 
>> Nhh, it's close..
>> 
>> I found that when I mount cgroup with -o freezer, self_checkpoint won't work.
>> It worked even I didn't mount the cgroup.
>> Is it what you expect?
> 
> No, it is not.  Can you tell us more about exactly how it fails?
> 

OK, I've checked differences of dmesg when self_restart does well and doesn't.
When it goes well, the filename is /tmp/cr-self.out

[  401.522556] [2307:2307:c/r:ckpt_read_fname:571] read filename '/tmp/cr-self.out'
[  401.522558] [2307:2307:c/r:restore_open_fname:594] fname '/tmp/cr-self.out' flags 0x2

However, when the contents of file remains, filename is /tmp/cr-self.out.org,
which is , of course, the one of original file binding to the original process.

[ 1088.414250] [2951:2951:c/r:ckpt_read_fname:571] read filename '/tmp/cr-self.out.orig'
[ 1088.414253] [2951:2951:c/r:restore_open_fname:594] fname '/tmp/cr-self.out.orig' flags 0x2

I can not reproduce yet, but at least cgroup freezer option won't affect like I mentioned.
Sorry that it might confuse you.

I still can not restart of external checkpoint.
I'll try to v20 next time.

> Maybe get the cr_tests (either from Oren's tree or from
> git clone git://git.sr71.net/~hallyn/cr_tests.git), cd cr_test,
> make, cd simple, run ./ckpt and send us the contents of
> /tmp/log, dmesg, and ckptinfo -ve /tmp/out ?

I think it runs OK, but send it in case.
/tmp/log was empty by the way.

thanks

>> Thank you again for the help!
>> I'm feeling better to use the latest ..
> 
> -serge
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