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

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Message-ID: <20211116072054.4d2129cb@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Tue, 16 Nov 2021 07:20:54 -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 07:05:54 -0800 Eric Dumazet wrote:
> 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.

Can't wait ! :)