netdev - Re: [PATCH net-next] net-sysfs: display two backlog queue len separately

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Message-ID: <20230312192847.0d58155e@hermes.local>
Date:   Sun, 12 Mar 2023 19:28:47 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Jason Xing <kerneljasonxing@...il.com>
Cc:     Simon Horman <simon.horman@...igine.com>, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next] net-sysfs: display two backlog queue len
 separately

On Mon, 13 Mar 2023 09:55:37 +0800
Jason Xing <kerneljasonxing@...il.com> wrote:

> On Mon, Mar 13, 2023 at 3:02 AM Simon Horman <simon.horman@...igine.com> wrote:
> >
> > On Sat, Mar 11, 2023 at 11:17:56PM +0800, Jason Xing wrote:  
> > > From: Jason Xing <kernelxing@...cent.com>
> > >
> > > Sometimes we need to know which one of backlog queue can be exactly
> > > long enough to cause some latency when debugging this part is needed.
> > > Thus, we can then separate the display of both.
> > >
> > > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > > ---
> > >  net/core/net-procfs.c | 17 ++++++++++++-----
> > >  1 file changed, 12 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/net/core/net-procfs.c b/net/core/net-procfs.c
> > > index 1ec23bf8b05c..97a304e1957a 100644
> > > --- a/net/core/net-procfs.c
> > > +++ b/net/core/net-procfs.c
> > > @@ -115,10 +115,14 @@ static int dev_seq_show(struct seq_file *seq, void *v)
> > >       return 0;
> > >  }
> > >
> > > -static u32 softnet_backlog_len(struct softnet_data *sd)
> > > +static u32 softnet_input_pkt_queue_len(struct softnet_data *sd)
> > >  {
> > > -     return skb_queue_len_lockless(&sd->input_pkt_queue) +
> > > -            skb_queue_len_lockless(&sd->process_queue);
> > > +     return skb_queue_len_lockless(&sd->input_pkt_queue);
> > > +}
> > > +
> > > +static u32 softnet_process_queue_len(struct softnet_data *sd)
> > > +{
> > > +     return skb_queue_len_lockless(&sd->process_queue);
> > >  }
> > >
> > >  static struct softnet_data *softnet_get_online(loff_t *pos)
> > > @@ -169,12 +173,15 @@ static int softnet_seq_show(struct seq_file *seq, void *v)
> > >        * mapping the data a specific CPU
> > >        */
> > >       seq_printf(seq,
> > > -                "%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x\n",
> > > +                "%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x "
> > > +                "%08x %08x\n",
> > >                  sd->processed, sd->dropped, sd->time_squeeze, 0,
> > >                  0, 0, 0, 0, /* was fastroute */
> > >                  0,   /* was cpu_collision */
> > >                  sd->received_rps, flow_limit_count,
> > > -                softnet_backlog_len(sd), (int)seq->index);
> > > +                0,   /* was len of two backlog queues */
> > > +                (int)seq->index,  
> >
> > nit: I think you could avoid this cast by using %llx as the format specifier.  
> 
> I'm not sure if I should change this format since the above line is
> introduced in commit 7d58e6555870d ('net-sysfs: add backlog len and
> CPU id to softnet data').
> The seq->index here manifests which cpu it uses, so it can be
> displayed in 'int' format. Meanwhile, using %8x to output is much
> cleaner if the user executes 'cat /proc/net/softnet_stat'.
> 
> What do you think about this?
> 
> Thanks,
> Jason

I consider sofnet_data a legacy API (ie don't change).
Why not add to real sysfs for network device with the one value per file?