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 07:05:54 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Jakub Kicinski <kuba@...nel.org>
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, Nov 16, 2021 at 6:27 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Mon, 15 Nov 2021 11:02:46 -0800 Eric Dumazet wrote:
> > One cpu can now be fully utilized for the kernel->user copy,
> > and another cpu is handling BH processing and skb/page
> > allocs/frees (assuming RFS is not forcing use of a single CPU)
>
> Are you saying the kernel->user copy is not under the socket lock
> today? I'm working on getting the crypto & copy from under the socket
> lock for ktls, and it looked like tcp does the copy under the lock.

Copy is done currently with socket lock owned.

But each skb is freed one at a time, after its payload has been consumed.

Note that I am also working on performing the copy while still allowing BH
to process incoming packets.

This is a bit more complex, but I think it is doable.