netdev - Re: [PATCH net-next] net/sched: get rid of qdisc->padded

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Message-ID: <20201009083838.0e9e91f8@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Fri, 9 Oct 2020 08:38:38 -0700
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>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Allen Pais <allen.lkml@...il.com>
Subject: Re: [PATCH net-next] net/sched: get rid of qdisc->padded

On Fri, 9 Oct 2020 09:35:03 +0200 Eric Dumazet wrote:
> On Fri, Oct 9, 2020 at 2:18 AM Jakub Kicinski <kuba@...nel.org> wrote:
> >
> > On Wed,  7 Oct 2020 09:51:11 -0700 Eric Dumazet wrote:  
> > > diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
> > > index 6c762457122fd0091cb0f2bf41bda73babc4ac12..d8fd8676fc724110630904909f64d7789f3a4b47 100644
> > > --- a/include/net/sch_generic.h
> > > +++ b/include/net/sch_generic.h
> > > @@ -91,7 +91,7 @@ struct Qdisc {
> > >       struct net_rate_estimator __rcu *rate_est;
> > >       struct gnet_stats_basic_cpu __percpu *cpu_bstats;
> > >       struct gnet_stats_queue __percpu *cpu_qstats;
> > > -     int                     padded;
> > > +     int                     pad;
> > >       refcount_t              refcnt;
> > >
> > >       /*  
> >
> > Hi Eric!
> >
> > Why keep the pad field? the member to lines down is
> > __cacheline_aligned, so we shouldn't have to manually
> > push things out?
> >
> >         struct gnet_stats_queue __percpu *cpu_qstats;
> >         int                     pad;  
> 
> I usually prefer adding explicit fields to tell where the holes are,
> for future reuse.
> Not many developers are aware of pahole existence :/
> I renamed it to pad, I could have used padding or something else.

Alright then, applied, thank you!