netdev - Re: [PATCH v1 net-next 3/5] netns-ipv4: reorganize netns

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Date: Wed, 20 Sep 2023 23:31:42 -0700
From: Coco Li <lixiaoyan@...gle.com>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
Cc: Jakub Kicinski <kuba@...nel.org>, Eric Dumazet <edumazet@...gle.com>, 
	Neal Cardwell <ncardwell@...gle.com>, Mubashir Adnan Qureshi <mubashirq@...gle.com>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, Chao Wu <wwchao@...gle.com>, 
	Wei Wang <weiwan@...gle.com>
Subject: Re: [PATCH v1 net-next 3/5] netns-ipv4: reorganize netns_ipv4 fast
 path variables

On Sun, Sep 17, 2023 at 10:10 AM Vadim Fedorenko
<vadim.fedorenko@...ux.dev> wrote:
>
> On 16/09/2023 02:06, Coco Li wrote:
> > Reorganize fast path variables on tx-txrx-rx order.
> > Fastpath cacheline ends after sysctl_tcp_rmem.
> > There are only read-only variables here. (write is on the control path
> > and not considered in this case)
>
> I believe udp sysctls can be aligned the same way. With HTTP/3 adoption
> we should think about UDP traffic too, and looks like we do have some
> space in hot-path cache lines for udp_early_demux and rmem/wmem.
>
> And have you thought about cache-line boundary alignment for these values?
>

Thank you for the suggestion!

The patch set was created and tested with TCP traffic in mind, and it
is really with the entire series that with TCP traffic we can see the
cpu per ops improvement, whereas it is difficult to measure
performance improvements of the individual patches including this one.

As you pointed out, there is still space in the hot cache line to fit
UDP traffic sysctls. We encourage folks to use this series and its
documentation as a template to add fast path network stack protocol
variables that are important to them :)