netdev - Re: [PATCH net-next 2/2] net: revert "Update RFS target at poll for tcp/udp"

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Message-Id: <20180105.111530.1134473876155222345.davem@davemloft.net>
Date:   Fri, 05 Jan 2018 11:15:30 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     soheil.kdev@...il.com
Cc:     netdev@...r.kernel.org, pjt@...gle.com, ycheng@...gle.com,
        soheil@...gle.com, willemb@...gle.com, edumazet@...gle.com,
        ncardwell@...gle.com
Subject: Re: [PATCH net-next 2/2] net: revert "Update RFS target at poll
 for tcp/udp"

From: Soheil Hassas Yeganeh <soheil.kdev@...il.com>
Date: Wed,  3 Jan 2018 21:47:11 -0500

> From: Soheil Hassas Yeganeh <soheil@...gle.com>
> 
> On multi-threaded processes, one common architecture is to have
> one (or a small number of) threads polling sockets, and a
> considerably larger pool of threads reading form and writing to the
> sockets. When we set RPS core on tcp_poll() or udp_poll() we essentially
> steer all packets of all the polled FDs to one (or small number of)
> cores, creaing a bottleneck and/or RPS misprediction.
> 
> Another common architecture is to shard FDs among threads pinned
> to cores. In such a setting, setting RPS core in tcp_poll() and
> udp_poll() is redundant because the RFS core is correctly
> set in recvmsg and sendmsg.
> 
> Thus, revert the following commit:
> c3f1dbaf6e28 ("net: Update RFS target at poll for tcp/udp").
> 
> Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Neal Cardwell <ncardwell@...gle.com>

Applied.