[Pvfs2-developers] Does this look right?

[Scott Atchley]

On Jan 2, 2007, at 5:11 PM, Sam Lang wrote:

> Cool to hear that this MX is working with PVFS.  I would like to  
> gather info about the assumptions we make (and that you had to  
> discover on your own) about the BMI API and semantics, so that we  
> can publish the process of adding BMI methods.  I'll try to walk  
> through the emails that you've sent to the list as and send  
> something out, but if you have a list of other 'gotchas' that you  
> could send, that would be great to start with.

I can't think of any at the moment. It would be helpful to describe  
the order of operations on the client versus the server (e.g.  
BMI_meth_method_addr_lookup() with an id on the server and not on the  
client, BMI_meth_method_addr_lookup() before initialize on the server  
and after on the client, etc.).

>> While copying the large file, I see a lot of expected messages  
>> arrive before the matching receive has been posted. I believe Sam  
>> or RobL mentioned that if there are multiple messages per  
>> operation, that the next receive is not posted until the previous  
>> receive is completed. Is that correct? If so, would it be possible  
>> to post all at once or would that break some of the other BMI  
>> methods?
>
> It wouldn't break BMI methods, and I think in most cases the  
> receives _should_ be posted around the same time as the sends.  Can  
> you give more details about the sizes and endpoints?  I'm guessing  
> that the side receiving expected messages before the receives are  
> posted is the server.  Is that the case?  Also, what sizes are the  
> messages?
>
> Thanks,
>
> -sam

One of the things we added to MX was an unexpected message callback  
handler. This allows me to use an active message model for certain  
messages (connection and unexpected). I ignore messages that should  
be expected (based on their match bits). I have not printed detailed  
info on the early expected messages, but I can print the tag and  
length (I am only using a single client and single server). I will do  
that Wednesday.

As for which side is seeing the early expected receives, it is the  
one on the receiving side of the bulk transfer. Copying from client  
to server, the server sees them and vice versa.

Scott