linux-kernel - Re: [PATCH] net-sysfs: export gso_max

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Date:   Fri, 24 Nov 2017 10:32:49 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Ahern <dsahern@...il.com>,
        Solio Sarabia <solio.sarabia@...el.com>,
        netdev@...r.kernel.org, davem@...eloft.net,
        stephen@...workplumber.org
Cc:     kys@...rosoft.com, shiny.sebastian@...el.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net-sysfs: export gso_max_size attribute

On Fri, 2017-11-24 at 10:14 -0700, David Ahern wrote:
> On 11/22/17 5:30 PM, Solio Sarabia wrote:
> > The netdevice gso_max_size is exposed to allow users fine-control
> > on
> > systems with multiple NICs with different GSO buffer sizes, and
> > where
> > the virtual devices like bridge and veth, need to be aware of the
> > GSO
> > size of the underlying devices.
> > 
> > In a virtualized environment, setting the right GSO sizes for
> > physical
> > and virtual devices makes all TSO work to be on physical NIC,
> > improving
> > throughput and reducing CPU util. If virtual devices send buffers
> > greater than what NIC supports, it forces host to do TSO for
> > buffers
> > exceeding the limit, increasing CPU utilization in host.
> > 
> > Suggested-by: Shiny Sebastian <shiny.sebastian@...el.com>
> > Signed-off-by: Solio Sarabia <solio.sarabia@...el.com>
> > ---
> 
> This should be added to rtnetlink rather than sysfs.

This is already exposed by rtnetlink [1]

Please lets not add yet another net-sysfs knob.

[1] c70ce028e834f8e51306217dbdbd441d851c64d3 net/rtnetlink: add IFLA_GSO_MAX_SEGS and IFLA_GSO_MAX_SIZE attributes