From: Jason Gunthorpe <jgg@nvidia.com>
To: Leon Romanovsky <leon@kernel.org>
Cc: Or Har-Toov <ohartoov@nvidia.com>,
linux-rdma@vger.kernel.org, Maher Sanalla <msanalla@nvidia.com>
Subject: Re: [PATCH rdma-next 3/3] IB/mad: Add flow control for solicited MADs
Date: Tue, 10 Dec 2024 16:12:29 -0400 [thread overview]
Message-ID: <20241210201229.GL2347147@nvidia.com> (raw)
In-Reply-To: <edea14a9da803479b986ba3a27058390891de21e.1733233636.git.leonro@nvidia.com>
On Tue, Dec 03, 2024 at 03:52:23PM +0200, Leon Romanovsky wrote:
> From: Or Har-Toov <ohartoov@nvidia.com>
>
> Currently, MADs sent via an agent are being forwarded directly to the
> corresponding MAD QP layer.
> MADs with a timeout value set and requiring a response (solicited MADs)
> will be resent if the timeout expires without receiving a response.
> In a congested subnet, flooding MAD QP layer with more solicited send
> requests from the agent will only worsen the situation by triggering
> more timeouts and therefore more retries.
This explanation does not really capture what this patch is supposed
to be doing. The point of solicited MADs is that they require a reply,
and the purpose of this patch is to try and conserve a reply slot in
the receive queue for the reply to land. Sending more requests than
the kernel has reply buffers is probably going to overflow the
HCA's receive queue.
Jason
prev parent reply other threads:[~2024-12-10 20:12 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-03 13:52 [PATCH rdma-next 0/3] Add Flow Control for Solicited MADs Leon Romanovsky
2024-12-03 13:52 ` [PATCH rdma-next 1/3] IB/mad: Replace MAD's refcount with a state machine Leon Romanovsky
2024-12-10 16:12 ` Jason Gunthorpe
2024-12-03 13:52 ` [PATCH rdma-next 2/3] IB/mad: Remove unnecessary done list by utilizing MAD states Leon Romanovsky
2024-12-10 19:00 ` Jason Gunthorpe
2024-12-10 23:51 ` Or Har-Toov
2024-12-03 13:52 ` [PATCH rdma-next 3/3] IB/mad: Add flow control for solicited MADs Leon Romanovsky
2024-12-10 20:12 ` Jason Gunthorpe [this message]
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