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Subject: Re: [OMPI devel] callback debugging
From: Ralph Castain (rhc_at_[hidden])
Date: 2014-01-21 10:27:32


That doesn't make any sense - I can't imagine a reason for orte-checkpoint itself to be running a barrier. I wonder if it is selecting the wrong component in snapc?

As for the patch, that isn't going to work. The collective id has to be *globally* unique, which means that only orterun can issue a new one. So you have to get thru orte_init before you can request one as it requires a communication.

However, like I said, it makes no sense for orte-checkpoint to do a barrier as it is a singleton - there is nothing for it to "barrier" with.

On Jan 21, 2014, at 7:24 AM, Adrian Reber <adrian_at_[hidden]> wrote:

> I think I still do not really understand how it works.
>
> The barrier on which orte-checkpoint is currently hanging is in
> app_coord_init(). You are also saying that orte-checkpoint
> should not be calling a barrier. The backtrace of the point where it
> is hanging now looks like:
>
> #0 0x00007ffff69befa0 in __nanosleep_nocancel () at ../sysdeps/unix/syscall-template.S:81
> #1 0x00007ffff7b45712 in app_coord_init () at ../../../../../orte/mca/snapc/full/snapc_full_app.c:208
> #2 0x00007ffff7b3a5ce in orte_snapc_full_module_init (seed=false, app=true) at ../../../../../orte/mca/snapc/full/snapc_full_module.c:207
> #3 0x00007ffff7b375de in orte_snapc_base_select (seed=false, app=true) at ../../../../orte/mca/snapc/base/snapc_base_select.c:96
> #4 0x00007ffff7a9884a in orte_ess_base_tool_setup () at ../../../../orte/mca/ess/base/ess_base_std_tool.c:192
> #5 0x00007ffff7a9fe85 in rte_init () at ../../../../../orte/mca/ess/tool/ess_tool_module.c:83
> #6 0x00007ffff7a4647f in orte_init (pargc=0x7fffffffd94c, pargv=0x7fffffffd940, flags=8) at ../../orte/runtime/orte_init.c:158
> #7 0x0000000000402859 in ckpt_init (argc=51, argv=0x7fffffffda78) at ../../../../orte/tools/orte-checkpoint/orte-checkpoint.c:610
> #8 0x0000000000401d7a in main (argc=51, argv=0x7fffffffda78) at ../../../../orte/tools/orte-checkpoint/orte-checkpoint.c:245
>
> Maybe I am doing something completely wrong. I am currently
> running 'orterun -np 2 test-programm'.
>
> In another terminal I am starting orte-checkpoint with the PID of
> orterun and the barrier in app_coord_init() is just before it tries
> to communicate with orterun. Is this the correct setup?
>
> Adrian
>
> On Mon, Jan 20, 2014 at 05:33:59PM -0600, Josh Hursey wrote:
>> If it is the application, then there is probably a barrier in the
>> app_coord_init() to make sure all the applications are up and running.
>> After this point then the global coordinator knows that the application can
>> be checkpointed.
>>
>> I don't think orte-checkpoint should be calling a barrier - from what I
>> recall.
>>
>>
>> On Mon, Jan 20, 2014 at 4:46 PM, Ralph Castain <rhc_at_[hidden]> wrote:
>>
>>> Is it orte-checkpoint that is hanging, or the app you are trying to
>>> checkpoint?
>>>
>>>
>>> On Jan 20, 2014, at 2:10 PM, Adrian Reber <adrian_at_[hidden]> wrote:
>>>
>>> Thanks for your help. I tried initializing the barrier correctly (see
>>> attached patch) but now, instead of crashing, it just hangs on the
>>> barrier while running orte-checkpoint
>>>
>>> [dcbz:20150] [[41665,0],0] grpcomm:bad entering barrier
>>> [dcbz:20150] [[41665,0],0] ACTIVATING GRCPCOMM OP 0 at
>>> ../../../../../orte/mca/grpcomm/bad/grpcomm_bad_module.c:206
>>>
>>> #0 0x00007ffff69befa0 in __nanosleep_nocancel () at
>>> ../sysdeps/unix/syscall-template.S:81
>>> #1 0x00007ffff7b456ba in app_coord_init () at
>>> ../../../../../orte/mca/snapc/full/snapc_full_app.c:207
>>> #2 0x00007ffff7b3a582 in orte_snapc_full_module_init (seed=false,
>>> app=true) at ../../../../../orte/mca/snapc/full/snapc_full_module.c:207
>>>
>>> it hangs looping at ORTE_WAIT_FOR_COMPLETION(coll->active);
>>>
>>> I do not understand on what the barrier here is actually waiting for. Where
>>> do I need to look to find the place the barrier is waiting for?
>>>
>>> I also tried initializing the collective id's in
>>> orte/mca/plm/base/plm_base_launch_support.c but that code is never
>>> used running the orte-checkpoint tool
>>>
>>> Adrian
>>>
>>> On Sat, Jan 11, 2014 at 11:46:42AM -0800, Ralph Castain wrote:
>>>
>>> I took a look at this, and I'm afraid you have some work to do in the
>>> orte/mca/snapc code base:
>>>
>>> 1. you must use dynamically allocated buffers for rml.send_buffer_nb. See
>>> r30261 for an example of the changes that need to be made - I did some, but
>>> can't swear to catching them all. It was enough to at least get a proc past
>>> the initial snapc registration
>>>
>>> 2. you are reusing collective id's to execute several orte_grpcomm.barrier
>>> calls - those ids are used elsewhere during MPI_Init. This is not allowed -
>>> a collective id can only be used *once*. What you need to do is go into
>>> orte/mca/plm/base/plm_base_launch_support.c and (when cr is configured) add
>>> cr-specific collective id's for this purpose. I don't know how many places
>>> in the cr code create their own barriers, but they each need a collective
>>> id.
>>>
>>> If you prefer and have the time, you are welcome to extend the collective
>>> code to allow id reuse. This would require that each daemon and app "reset"
>>> the collective fields when a collective is declared complete. It isn't that
>>> hard to do - just never had a reason to do it. I can take a shot at it when
>>> time permits (may have some time this weekend)
>>>
>>> 3. when you post the non-blocking recv in the snapc/full code, it looks to
>>> me like you need to block until you get the answer. I don't know where in
>>> the code flow this is occurring - if you are not in an event, then it is
>>> okay to block using ORTE_WAIT_FOR_COMPLETION. Look in
>>> orte/mca/routed/base/routed_base_fns.c starting at line 252 for an example.
>>>
>>> HTH
>>> Ralph
>>>
>>> On Jan 10, 2014, at 12:55 PM, Ralph Castain <rhc_at_[hidden]> wrote:
>>>
>>>
>>> On Jan 10, 2014, at 12:45 PM, Adrian Reber <adrian_at_[hidden]> wrote:
>>>
>>> On Fri, Jan 10, 2014 at 09:48:14AM -0800, Ralph Castain wrote:
>>>
>>>
>>> On Jan 10, 2014, at 8:02 AM, Adrian Reber <adrian_at_[hidden]> wrote:
>>>
>>> I am currently trying to understand how callbacks are working. Right now
>>> I am looking at orte/mca/rml/base/rml_base_receive.c
>>> orte_rml_base_comm_start() which does
>>>
>>> orte_rml.recv_buffer_nb(ORTE_NAME_WILDCARD,
>>> ORTE_RML_TAG_RML_INFO_UPDATE,
>>> ORTE_RML_PERSISTENT,
>>> orte_rml_base_recv,
>>> NULL);
>>>
>>> As far as I understand it orte_rml_base_recv() is the callback function.
>>> At which point should this function run? When the data is actually
>>> received?
>>>
>>>
>>> Not precisely. When data is received by the OOB, it pushes the data into
>>> an event. When that event gets serviced, it calls the orte_rml_base_receive
>>> function which processes the data to find the matching tag, and then uses
>>> that to execute the callback to the user code.
>>>
>>>
>>> The same for send_buffer_nb() functions. I do not see the callback
>>> functions actually running. How can I verify that the callback functions
>>> are running. Especially for the send case it sounds pretty obvious how
>>> it should work but I never see the callback function running. At least
>>> in my setup.
>>>
>>>
>>> The data is not immediately sent. It gets pushed into an event. When that
>>> event gets serviced, it calls the orte_oob_base_send function which then
>>> passes the data to each active OOB component until one of them says it can
>>> send it. The data is then pushed into another event to get it into the
>>> event base for that component's active module - when that event gets
>>> serviced, the data is sent. Once the data is sent, an event is created
>>> that, when serviced, executes the callback to the user code.
>>>
>>> If you aren't seeing callbacks, the most likely cause is that the orte
>>> progress thread isn't running. Without it, none of this will work.
>>>
>>>
>>> Thanks. Running configure without '--with-ft=cr' I can run a program and
>>> use orte-top. In orterun I can see that the callback is running and
>>> orte-top displays the retrieved information. I can also see in orte-top
>>> that the callbacks are working.
>>>
>>>
>>> Actually, I'm rather impressed - I hadn't tested orte-top and didn't
>>> honestly know if it would work any more! Glad to hear it does :-)
>>>
>>> Doing the same with '--with-ft=cr'
>>> enabled orte-top crashes as well as orte-checkpoint and both (-top and
>>> -checkpoint) seem to no longer have working callbacks and that is why
>>> they are probably crashing. So some code which is enabled by '--with-ft=cr'
>>> seems to break callbacks in orte-top as well as in orte-checkpoint.
>>> orterun handles callbacks no matter if configured with or without
>>> '--with-ft=cr'.
>>>
>>>
>>> I can take a look this weekend - probably something silly
>>>
>>>
>>> Adrian
>>>
>>> <grpcomm.txt>_______________________________________________
>>>
>>> devel mailing list
>>> devel_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>>>
>>>
>>>
>>> _______________________________________________
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>>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>>>
>>
>>
>>
>> --
>> Joshua Hursey
>> Assistant Professor of Computer Science
>> University of Wisconsin-La Crosse
>> http://cs.uwlax.edu/~jjhursey
>
>> _______________________________________________
>> devel mailing list
>> devel_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>
>
> Adrian
>
> --
> Adrian Reber <adrian_at_[hidden]> http://lisas.de/~adrian/
> QOTD:
> "I tried buying a goat instead of a lawn tractor; had to return
> it though. Couldn't figure out a way to connect the snow blower."
> _______________________________________________
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