Subject: Re: [PATCH net-next] net: sysfs: Do not create sysfs for non BQL device

From: Breno Leitao <[email-masked]>
Date: Thu, 15 Feb 2024 05:11:26 -0800

On Thu, Feb 15, 2024 at 01:47:47PM +0100, Eric Dumazet wrote:
> On Thu, Feb 15, 2024 at 12:28 PM Breno Leitao <[email-masked]> wrote:
> >
> > Creation of sysfs entries is expensive, mainly for workloads that
> > constantly creates netdev and netns often.
> >
> > Do not create BQL sysfs entries for devices that don't need,
> > basically those that do not have a real queue, i.e, devices that has
> > NETIF_F_LLTX and IFF_NO_QUEUE, such as `lo` interface.
> >
> > This will remove the /sys/class/net/eth0/queues/tx-X/byte_queue_limits/
> > directory for these devices.
> >
> > In the example below, eth0 has the `byte_queue_limits` directory but not
> > `lo`.
> >
> >         # ls /sys/class/net/lo/queues/tx-0/
> >         traffic_class  tx_maxrate  tx_timeout  xps_cpus  xps_rxqs
> >
> >         # ls /sys/class/net/eth0/queues/tx-0/byte_queue_limits/
> >         hold_time  inflight  limit  limit_max  limit_min
> >
> > Suggested-by: Eric Dumazet <[email-masked]>
> > Signed-off-by: Breno Leitao <[email-masked]>
> > ---
> >  net/core/net-sysfs.c | 23 ++++++++++++++++++-----
> >  1 file changed, 18 insertions(+), 5 deletions(-)
> >
> > diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> > index a09d507c5b03..c79bc11a0347 100644
> > --- a/net/core/net-sysfs.c
> > +++ b/net/core/net-sysfs.c
> > @@ -1417,6 +1417,15 @@ static ssize_t bql_show_inflight(struct netdev_queue *queue,
> >         return sysfs_emit(buf, "%u\n", dql->num_queued - dql->num_completed);
> >  }
> >
> > +static bool netdev_uses_bql(struct net_device *dev)
> 
>   const struct net_device *dev

Thanks. I will update and incorporate it in a v2 (that I am planning to
send tomorrow).