net-sysfs: add backlog len and CPU id to softnet data

Currently the backlog status in not exposed to user-space.
Since long backlogs (or simply not empty ones) can be a
source of noticeable latency, -RT deployments need some way
to inspect it.

Additionally, there isn't a direct match between 'softnet_stat'
lines and the related CPU - sd for offline CPUs are not dumped -
so this patch also includes the CPU id into such entry.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/net-procfs.c b/net/core/net-procfs.c
index 6bbd06f..c714e6a 100644 (file)
--- a/net/core/net-procfs.c
+++ b/net/core/net-procfs.c
@@ -116,6 +116,12 @@ static int dev_seq_show(struct seq_file *seq, void *v)
        return 0;
 }
 
+static u32 softnet_backlog_len(struct softnet_data *sd)
+{
+       return skb_queue_len_lockless(&sd->input_pkt_queue) +
+              skb_queue_len_lockless(&sd->process_queue);
+}
+
 static struct softnet_data *softnet_get_online(loff_t *pos)
 {
        struct softnet_data *sd = NULL;
@@ -159,12 +165,17 @@ static int softnet_seq_show(struct seq_file *seq, void *v)
        rcu_read_unlock();
 #endif
 
+       /* the index is the CPU id owing this sd. Since offline CPUs are not
+        * displayed, it would be othrwise not trivial for the user-space
+        * mapping the data a specific CPU
+        */
        seq_printf(seq,
-                  "%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\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);
+                  sd->received_rps, flow_limit_count,
+                  softnet_backlog_len(sd), (int)seq->index);
        return 0;
 }