[Pvfs2-developers] BMI initial contact between new peers

[Sam Lang]

Hi Scott,

Scott Atchley wrote:
> Hi all,
> 
> From what I understand, PVFS does not have a notion of a client and
> server maintaining any connection state. The client will simply send an
> unexpected message to the server that may or may not be followed by a
> series of expected sends between the two.

Yes that's correct.

> 
> Since clients initiate all first contact with the servers, what is the
> standard procedure? Send an unexpected message only or post a receive
> and then send an unexpected message and wait for an expected send from
> the server?

The latter.

> 
> I am trying to determine whether a send or receive is posted first for a
> new peer.

The msgpairarray state machine in src/common/misc/msgpairarray.sm is the
engine for most of the request/response style unexpected messages from
client to server.  The msgpairarray_post function first calls
job_bmi_recv which posts the receive (calls BMI_post_recv), and then
calls job_bmi_send_list, which basically translates to calling
BMI_post_sendunexpected_list.

> 
> Also, can more than one BMI method be called at anyone time (e.g.
> concurrent send and/or recvs)?

Yes.  All the BMI calls are non-blocking, and we often post many
receives and sends and let the test call drive completion of them.

-sam

> 
> Scott
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