netdev - Re: [PATCH net-next v2] net/smc: Reduce overflow of smc clcsock listen queue

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Message-ID: <d35569df-e0e0-5ea7-9aeb-7ffaeef04b14@linux.ibm.com>
Date:   Wed, 5 Jan 2022 20:13:23 +0100
From:   Karsten Graul <kgraul@...ux.ibm.com>
To:     "D. Wythe" <alibuda@...ux.alibaba.com>
Cc:     dust.li@...ux.alibaba.com, kuba@...nel.org, davem@...emloft.net,
        netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-rdma@...r.kernel.org
Subject: Re: [PATCH net-next v2] net/smc: Reduce overflow of smc clcsock
 listen queue

On 05/01/2022 16:06, D. Wythe wrote:
> LGTM. Fallback makes the restrictions on SMC dangling
> connections more meaningful to me, compared to dropping them.
> 
> Overall, i see there are two scenario.
> 
> 1. Drop the overflow connections limited by userspace application
> accept.
> 
> 2. Fallback the overflow connections limited by the heavy process of
> current SMC handshake. ( We can also control its behavior through
> sysctl.)
> 

I vote for (2) which makes the behavior from user space applications point of view more like TCP.

One comment to sysctl: our current approach is to add new switches to the existing 
netlink interface which can be used with the smc-tools package (or own implementations of course). 
Is this prereq problematic in your environment? 
We tried to avoid more sysctls and the netlink interface keeps use more flexible.