netdev - Re: [PATCH net-next V1] net: adjust net_device layout for cacheline usage

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Message-ID: <20210212164900.53a9a452@carbon>
Date:   Fri, 12 Feb 2021 16:49:00 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Ahern <dsahern@...il.com>, netdev@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, bpf@...r.kernel.org,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        brouer@...hat.com
Subject: Re: [PATCH net-next V1] net: adjust net_device layout for cacheline
 usage

On Fri, 29 Jan 2021 15:00:58 +0100
Jesper Dangaard Brouer <brouer@...hat.com> wrote:

> On Fri, 29 Jan 2021 14:33:02 +0100
> Eric Dumazet <eric.dumazet@...il.com> wrote:
> 
> > On 1/26/21 6:39 PM, Jesper Dangaard Brouer wrote:  
> > > The current layout of net_device is not optimal for cacheline usage.
> > > 
[...]
> > > @@ -1877,6 +1876,23 @@ struct net_device {
[...]
> > > +
> > >  	netdev_features_t	features;
> > >  	netdev_features_t	hw_features;
> > >  	netdev_features_t	wanted_features;    
> > 
> > Probably wanted_features, hw_features are not used in fast path, only
> > in control path ?  
> 
> Yes, that was also my analysis.  I did consider moving those down, but
> I wanted to keep the first iteration simple ;-)

I've send a followup[1] to address this, thanks for pointing it out.

[1] https://patchwork.kernel.org/project/netdevbpf/patch/161313782625.1008639.6000589679659428869.stgit@firesoul/
-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer