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Date:   Sun, 9 Feb 2020 16:57:36 +0200
From:   Leon Romanovsky <leon@kernel.org>
To:     Dimitris Dimitropoulos <d.dimitropoulos@imatrex.com>
Cc:     linux-rdma@vger.kernel.org
Subject: Re: maximum QP size
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On Thu, Feb 06, 2020 at 09:18:00PM -0800, Dimitris Dimitropoulos wrote:
> Hi,
>
> I'm running the ibv_rc_pingpong example and I notice as as rx-depth
> increases the QP create fails, eg at 50k. My understanding is this
> variable controls the number of RECV WR that will be posted in advance
> before SEND WRs are posted.
>
> Is there a limitation on the queue size (the size is unit32_t) and if
> so why ? Also is there a way around it ?

The rx-depth is translated to the size of completion queue buffer.
That buffer used by hardware to post completions - writing completion
queue elements (CQEs) and it is allocated when creating the CQ.

Maximum number of CQEs can be retrieved by the ibv_devinfo -v, see max_cqe field.

Thanks

>
> Regards
> Dimitris