netdev - Re: [PATCH net-next 17/20] tcp: defer skb freeing after socket lock is released

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Date:   Tue, 16 Nov 2021 10:18:49 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Arjun Roy <arjunroy@...gle.com>
Subject: Re: [PATCH net-next 17/20] tcp: defer skb freeing after socket lock
 is released

On Tue, 16 Nov 2021 08:46:37 -0800 Eric Dumazet wrote:
> On my testing host,
> 
> 4K MTU : processing ~2,600.000 packets per second in GRO and other parts
> use about 60% of the core in BH.
> (Some of this cost comes from a clang issue, and the csum_partial() one
> I was working on last week)
> NIC RX interrupts are firing about 25,000 times per second in this setup.
> 
> 1500 MTU : processing ~ 5,800,000 packets per second uses one core in
> BH (and also one core in recvmsg()),
> We stay in NAPI mode (no IRQ rearming)
> (That was with a TCP_STREAM run sustaining 70Gbit)
> 
> BH numbers also depend on IRQ coalescing parameters.

Very interesting, curious to see what not doing the copy under socket
lock will do to the 1.5k case. 

Thanks a lot for sharing the detailed info!