netdev - Re: [RFC PATCH] net: Introduce a socket option to enable picking tx queue based on rx queue.

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Message-ID: <87vakdbd5k.fsf@stressinduktion.org>
Date:   Wed, 20 Sep 2017 17:30:47 +0200
From:   Hannes Frederic Sowa <hannes@...essinduktion.org>
To:     Sridhar Samudrala <sridhar.samudrala@...el.com>
Cc:     alexander.h.duyck@...el.com, netdev@...r.kernel.org
Subject: Re: [RFC PATCH] net: Introduce a socket option to enable picking tx queue based on rx queue.

Sridhar Samudrala <sridhar.samudrala@...el.com> writes:

> This patch introduces a new socket option SO_SYMMETRIC_QUEUES that can be used
> to enable symmetric tx and rx queues on a socket.
>
> This option is specifically useful for epoll based multi threaded workloads
> where each thread handles packets received on a single RX queue . In this model,
> we have noticed that it helps to send the packets on the same TX queue
> corresponding to the queue-pair associated with the RX queue specifically when
> busy poll is enabled with epoll().
>
> Two new fields are added to struct sock_common to cache the last rx ifindex and
> the rx queue in the receive path of an SKB. __netdev_pick_tx() returns the cached
> rx queue when this option is enabled and the TX is happening on the same device.

Would it help to make the rx and tx skb hashes symmetric
(skb_get_hash_symmetric) on request?