netdev - Re: [PATCH net-next] net: rfs: add sock_rps_delete

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Message-ID: <CADVnQykngURxudFtaH+vYs1k7P+udzhhnQiG9Wjbd8pfu6cMbA@mail.gmail.com>
Date: Thu, 15 May 2025 08:04:38 -0400
From: Neal Cardwell <ncardwell@...gle.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, Octavian Purdila <tavip@...gle.com>
Subject: Re: [PATCH net-next] net: rfs: add sock_rps_delete_flow() helper

On Thu, May 15, 2025 at 6:04 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> RFS can exhibit lower performance for workloads using short-lived
> flows and a small set of 4-tuple.
>
> This is often the case for load-testers, using a pair of hosts,
> if the server has a single listener port.
>
> Typical use case :
>
> Server : tcp_crr -T128 -F1000 -6 -U -l30 -R 14250
> Client : tcp_crr -T128 -F1000 -6 -U -l30 -c -H server | grep local_throughput
>
> This is because RFS global hash table contains stale information,
> when the same RSS key is recycled for another socket and another cpu.
>
> Make sure to undo the changes and go back to initial state when
> a flow is disconnected.
>
> Performance of the above test is increased by 22 %,
> going from 372604 transactions per second to 457773.
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Octavian Purdila <tavip@...gle.com>
> ---

Reviewed-by: Neal Cardwell <ncardwell@...gle.com>

Thanks, Eric!

neal