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SubjectRe: Linux Checkpoint-Restart - v19
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Hi,
On 2010/03/18, at 5:55, Serge E. Hallyn wrote:

> Quoting Jiro SEKIBA (jir@dependable-os.net):
>> Hi,
>>
>> Thank you for prompt reply!
>> Sorry that I didn't post to containers@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@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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