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

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Date:   Mon, 13 Mar 2023 09:55:37 +0800
From:   Jason Xing <kerneljasonxing@...il.com>
To:     Simon Horman <simon.horman@...igine.com>
Cc:     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, 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

>
> > +                softnet_input_pkt_queue_len(sd), softnet_process_queue_len(sd));
> >       return 0;
> >  }
> >
> > --
> > 2.37.3
> >