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Subject: Re: [OMPI devel] RFC: System V Shared Memory for Open MPI
From: Samuel K. Gutierrez (samuel_at_[hidden])
Date: 2010-06-02 13:07:38

Hi George,

That may work - I'll try it.


Samuel K. Gutierrez
Los Alamos National Laboratory
On Jun 2, 2010, at 10:59 AM, George Bosilca wrote:
> How about ftok ? The init function takes a file_name as argument,  
> and this file name is unique per instance of the shared memory  
> region we want to create. We can use this file name with ftok to  
> create a unique key_t that can be used by shmget to retrieve the  
> shared memory identifier.
>  george.
> On Jun 2, 2010, at 11:53 , Samuel K. Gutierrez wrote:
>> On Jun 2, 2010, at 8:49 AM, Jeff Squyres wrote:
>>> On Jun 2, 2010, at 10:44 AM, George Bosilca wrote:
>>>>> Not sure what you mean here.  common/sm may create new shmem  
>>>>> segments at any time (e.g., during coll sm).  The RML message  
>>>>> exchange is to ensure that only 1 process creates and  
>>>>> initializes the segment and then all the others just attach to it.
>>>> Absolutely not! The RML messaging is not about initializing the  
>>>> shared memory segment. As stated on my original text it has only  
>>>> one purpose: to ensure the file used by mmap is created  
>>>> atomically. The code for Windows do not exchange any RML messages  
>>>> as the function to allocate the shared memory region provided by  
>>>> the OS is atomic (exactly as the sysv one).
>>> I thought that Sam said that it was important that only 1 process  
>>> shmctl/IPC_RMID...?
>> Hi George,
>> We are using RML messaging in the sysv code to exchange the shared  
>> memory ID (generated by exactly one process).  I'm not sure how we  
>> would go about passing along the shared memory ID without RML, but  
>> any ideas are greatly appreciated.
>> Thanks,
>> --
>> Samuel K. Gutierrez
>> Los Alamos National Laboratory
>>> -- 
>>> Jeff Squyres
>>> jsquyres_at_[hidden]
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