[Lustre-devel] How can the name_to_handle() syscall benefit Lustre

[Lustre-devel] How can the name_to_handle() syscall benefit Lustre

[Vilobh Meshram]

Hi All,

How can the name_to_handle() syscall benefit Lustre ?

Any insights will be helpful.

Thanks,
Vilobh
*Graduate Research Associate
Department of Computer Science
The Ohio State University Columbus Ohio*
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[Lustre-devel] How can the name_to_handle() syscall benefit Lustre

[Andreas Dilger]

This is something that I think would be very useful for Lustre in conjunction with the Lustre MPI ADIO driver. The MPI rank-0 node could do the path traversal and generate a file handle via name_to_handle() and then MPI broadcast the file handle to all of the other MPI processes, which can use it to open the shared file. This could save many thousands of MDS RPCs to do path traversal for each client in a large MPI job. 

Cheers, Andreas

On 2011-01-29, at 12:16, Vilobh Meshram <vilobh.meshram@gmail.com> wrote:

> Hi All,
> 
> How can the name_to_handle() syscall benefit Lustre ?
> 
> Any insights will be helpful.
> 
> Thanks,
> Vilobh
> Graduate Research Associate
> Department of Computer Science
> The Ohio State University Columbus Ohio
> _______________________________________________
> Lustre-devel mailing list
> Lustre-devel at lists.lustre.org
> http://lists.lustre.org/mailman/listinfo/lustre-devel
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[Lustre-devel] How can the name_to_handle() syscall benefit Lustre

[James Simmons]

> This is something that I think would be very useful for Lustre in conjunction with the Lustre MPI ADIO driver. The MPI rank-0 node
> could do the path traversal and generate a file handle via name_to_handle() and then MPI broadcast the file handle to all of the
> other MPI processes, which can use it to open the shared file. This could save many thousands of MDS RPCs to do path traversal for
> each client in a large MPI job.?

I thought the name_to_handle syscall idea was shot down? 
 
> Cheers, Andreas
> 
> On 2011-01-29, at 12:16, Vilobh Meshram <vilobh.meshram@gmail.com> wrote:
> 
>       Hi All,
> How can the name_to_handle() syscall benefit Lustre ?
> 
> Any insights will be helpful.
> 
> Thanks,
> Vilobh
> Graduate Research Associate
> Department of Computer Science
> The Ohio State University Columbus Ohio
> 
>       _______________________________________________
>       Lustre-devel mailing list
>       Lustre-devel at lists.lustre.org
>       http://lists.lustre.org/mailman/listinfo/lustre-devel
> 
> 
> 

[Lustre-devel] How can the name_to_handle() syscall benefit Lustre

[Andreas Dilger]

On 2011-01-31, at 09:52, James Simmons wrote:
> Andreas Dilger wrote:
>> This is something that I think would be very useful for Lustre in conjunction with the Lustre MPI ADIO driver. The MPI rank-0 node
>> could do the path traversal and generate a file handle via name_to_handle() and then MPI broadcast the file handle to all of the
>> other MPI processes, which can use it to open the shared file. This could save many thousands of MDS RPCs to do path traversal for
>> each client in a large MPI job. 
> 
> I thought the name_to_handle syscall idea was shot down? 

I don't think it was shot down, as much as it hasn't yet been accepted.  I've tried to support it in a form that would be useful to Lustre/MPI, and while it isn't quite where I'd like it to be, I think the flaws in the implementation are not insurmountable.

The current proposal is lacking a well-defined permanent filesystem identifier in each handle (i.e. a UUID as part of the public fh structure), but I think Lustre can still include the UUID as part of the private fh and have the userspace code map that back to a specific Lustre mountpoint, since it would be implemented as part of the Lustre ADIO layer.

>> On 2011-01-29, at 12:16, Vilobh Meshram <vilobh.meshram@gmail.com> wrote:
>> How can the name_to_handle() syscall benefit Lustre ?
>> 
>> Any insights will be helpful.
>> 
>> Thanks,
>> Vilobh
>> Graduate Research Associate
>> Department of Computer Science
>> The Ohio State University Columbus Ohio
>> 
>>      _______________________________________________
>>      Lustre-devel mailing list
>>      Lustre-devel at lists.lustre.org
>>      http://lists.lustre.org/mailman/listinfo/lustre-devel
>> 
>> 
>> 


Cheers, Andreas
--
Andreas Dilger 
Principal Engineer
Whamcloud, Inc.