[ofa-general] MLX HCA: CQ request notification for multiple completions not implemented?

[Yicheng Jia]

Thanks for your reply. I'm using one CQ for all the WRs. Do you know why 
there's no ARM-N support in MLX drivers? My concern is the performance. 
The overhead of software poll_cq loop is quite significant if there are 
multiple pieces of small amount of data to be transferred on both 
sender/receiver sides. For instance, on the sender, the data I have are 
1k, 1k, 2k, 1k..., on the receiver side, the data size and blocks are the 
same, 1k, 1k, 2k, 1k.... Do you have a good solution for such kind of 
problem?

Best,
Yicheng




Dotan Barak <dotanba at gmail.com> 
05/23/2008 01:27 PM

To
Yicheng Jia <YJia at tmriusa.com>
cc
general at lists.openfabrics.org
Subject
Re: [ofa-general] MLX HCA: CQ request notification for multiple 
completions not implemented?






Hi.

Yicheng Jia wrote:
>
> Hi Folks,
>
> I'm trying to use CQ Event notification for multiple completions 
> (ARM_N) according to Mellanox Lx III user manual for scatter/gathering 
> RDMA. However I couldn't find it in current MLX driver. It seems to me 
> that only ARM_NEXT and ARM_SOLICIT are implemented. So if there are 
> multiple work requests, I have to use "poll_cq" to synchronously wait 
> until all the requests are done, is it correct? Is there a way to do 
> asynchronous multiple send by subscribing for a ARM_N event?
You are right: the low level drivers of Mellanox devices doesn't support 
ARM-N
(This feature is supported by the devices, but it wasn't implemented in 
the low level drivers).

You are right, in order to read all of the completions you need to use 
poll_cq.

By the way: Do you have you have to create a completion for any WR?
(if you are using one QP, this will maybe solve your problem).

Dotan

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