Re: [PATCH net-next v3] net/core: Export dev_core_stats_*_inc()

[Yajun Deng]

On 2023/9/14 23:22, Alexander Lobakin wrote:
> From: Yajun Deng <yajun.deng@xxxxxxxxx>
> Date: Thu, 14 Sep 2023 10:37:18 +0800
>
> > Although there is a kfree_skb_reason() helper function that can be used to
> > find the reason why this skb is dropped, but most callers didn't increase
> > one of rx_dropped, tx_dropped, rx_nohandler and rx_otherhost_dropped.
> >
> > For the users, people are more concerned about why the dropped in ip
> > is increasing. So we can export dev_core_stats_rx_dropped_inc sets,
> > which users would trace them know why rx_dropped is increasing.
> >
> > Export dev_core_stats_{rx_dropped, tx_dropped, rx_nohandler,
> > rx_otherhost_dropped}_inc for trace. Also, move dev_core_stats()
> > and netdev_core_stats_alloc() to dev.c, as they are not called
> > externally.
> I'd like to hear some arguments against having them static inlines + one
> external that I proposed earlier.

I'd like to hear suggestions from the maintainers. If the maintainers 
have no objections, I'd like to

use your approach.

> > Signed-off-by: Yajun Deng <yajun.deng@xxxxxxxxx>
> > ---
> > v3: __cold should be added to the netdev_core_stats_alloc().
> > v2: use __cold instead of inline in dev_core_stats().
> > v1: https://lore.kernel.org/netdev/20230911082016.3694700-1-yajun.deng@xxxxxxxxx/
> ...as it's not at least mentioned here in the changelog.
>
> [...]
>
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index ccff2b6ef958..98592e4c1df0 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -10475,7 +10475,7 @@ void netdev_stats_to_stats64(struct rtnl_link_stats64 *stats64,
> >   }
> >   EXPORT_SYMBOL(netdev_stats_to_stats64);
> >   
> > -struct net_device_core_stats __percpu *netdev_core_stats_alloc(struct net_device *dev)
> > +static __cold struct net_device_core_stats __percpu *netdev_core_stats_alloc(struct net_device *dev)
> This is way over 79/80 chars, break the line before "netdev_".
Okay.
> >   {
> >   	struct net_device_core_stats __percpu *p;
> >   
> > @@ -10488,7 +10488,35 @@ struct net_device_core_stats __percpu *netdev_core_stats_alloc(struct net_device
> >   	/* This READ_ONCE() pairs with the cmpxchg() above */
> >   	return READ_ONCE(dev->core_stats);
> >   }
> > -EXPORT_SYMBOL(netdev_core_stats_alloc);
> > +
> > +static inline struct net_device_core_stats __percpu *dev_core_stats(struct net_device *dev)
> Same for the line length.
> Also notice that now some of the functions you touch have "dev_" prefix,
> others have "netdev_", I'd probably take a look into unifying this.
Okay, I'll unify with the "netdev_" prefix.
> (note for the maintainers that it would be probably better to leave
>   explicit "inline" here, but no bloat-o-meter was provided by the
>   author, so I can't say anything for sure)
>
> > +{
> > +	/* This READ_ONCE() pairs with the write in netdev_core_stats_alloc() */
> > +	struct net_device_core_stats __percpu *p = READ_ONCE(dev->core_stats);
> > +
> > +	if (likely(p))
> > +		return p;
> > +
> > +	return netdev_core_stats_alloc(dev);
> > +}
> [...]
>
> Thanks,
> Olek