[rds-devel] [ofa-general] [PATCH RFC] rds: add iwarp support

[Olaf Kirch]

On Friday 04 July 2008 11:13:16 Olaf Kirch wrote:
> Okay, I re-read the fastreg patch. So it seems what you want to do is to
> allocate the fastreg_mr once, and remap it several times. Correct?
> Then this fits the current model quite well, except that we need
> to splice the whole thing into the send cq handling (so that we
> get told when the MR was mapped).

There's another problem with the approach chosen here. The iwarp rdma
code will try to post the two WRs directly to the send WQ. This will
confuse the book-keeping done in ib_send.c, where we assume we can
post new WRs to the send queue as long as we're able to allocate
WRs from the send ring. (Note how we set up the send WQ having
a size of the send ring + 1 - where the +1 is for the ACK WR).

So if you just post WRs to the send CQ, you create two problems -
 1.	your ib_post_send may fail, so you need to deal with this
 2.	someone else's ib_post_send in ib_send.c may fail, and
	that will confuse the code greatly.

So you really need to go through the ib_send code and allocate WRs
there, and wait if you can't get any... that gets icky fast.

Olaf
-- 
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