Subject: [RFC net-next 2/3] netdev: add queue stat for alloc failures

From: Jakub Kicinski <[email-masked]>
Date: Thu, 22 Feb 2024 14:36:28 -0800

Rx alloc failures are commonly counted by drivers.
Support reporting those via netdev-genl queue stats.

Signed-off-by: Jakub Kicinski <[email-masked]>
---
 Documentation/netlink/specs/netdev.yaml | 7 +++++++
 include/net/netdev_queues.h             | 2 ++
 include/uapi/linux/netdev.h             | 1 +
 net/core/netdev-genl.c                  | 3 ++-
 tools/include/uapi/linux/netdev.h       | 1 +
 5 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml
index eea41e9de98c..ea7b3b72b212 100644
--- a/Documentation/netlink/specs/netdev.yaml
+++ b/Documentation/netlink/specs/netdev.yaml
@@ -328,6 +328,13 @@ name: netdev
         name: tx-bytes
         doc: Successfully sent bytes, see `tx-packets`.
         type: uint
+      -
+        name: rx-alloc-fail
+        doc: |
+          Number of times skb or buffer allocation failed on the Rx datapath.
+          Allocation failure may, or may not result in a packet drop, depending
+          on driver implementation and whether system recovers quickly.
+        type: uint
 
 operations:
   list:
diff --git a/include/net/netdev_queues.h b/include/net/netdev_queues.h
index d633347eeda5..1ec408585373 100644
--- a/include/net/netdev_queues.h
+++ b/include/net/netdev_queues.h
@@ -4,9 +4,11 @@
 
 #include <linux/netdevice.h>
 
+/* See the netdev.yaml spec for definition of each statistic */
 struct netdev_queue_stats_rx {
 	u64 bytes;
 	u64 packets;
+	u64 alloc_fail;
 };
 
 struct netdev_queue_stats_tx {
diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
index c6a5e4b03828..ec65790c2c6c 100644
--- a/include/uapi/linux/netdev.h
+++ b/include/uapi/linux/netdev.h
@@ -146,6 +146,7 @@ enum {
 	NETDEV_A_STATS_RX_BYTES,
 	NETDEV_A_STATS_TX_PACKETS,
 	NETDEV_A_STATS_TX_BYTES,
+	NETDEV_A_STATS_RX_ALLOC_FAIL,
 
 	__NETDEV_A_STATS_MAX,
 	NETDEV_A_STATS_MAX = (__NETDEV_A_STATS_MAX - 1)
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index fe4e9bc5436a..7976c112c447 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -498,7 +498,8 @@ static int
 netdev_nl_stats_write_rx(struct sk_buff *rsp, struct netdev_queue_stats_rx *rx)
 {
 	if (netdev_stat_put(rsp, NETDEV_A_STATS_RX_PACKETS, rx->packets) ||
-	    netdev_stat_put(rsp, NETDEV_A_STATS_RX_BYTES, rx->bytes))
+	    netdev_stat_put(rsp, NETDEV_A_STATS_RX_BYTES, rx->bytes) ||
+	    netdev_stat_put(rsp, NETDEV_A_STATS_RX_ALLOC_FAIL, rx->alloc_fail))
 		return -EMSGSIZE;
 	return 0;
 }
diff --git a/tools/include/uapi/linux/netdev.h b/tools/include/uapi/linux/netdev.h
index c6a5e4b03828..ec65790c2c6c 100644
--- a/tools/include/uapi/linux/netdev.h
+++ b/tools/include/uapi/linux/netdev.h
@@ -146,6 +146,7 @@ enum {
 	NETDEV_A_STATS_RX_BYTES,
 	NETDEV_A_STATS_TX_PACKETS,
 	NETDEV_A_STATS_TX_BYTES,
+	NETDEV_A_STATS_RX_ALLOC_FAIL,
 
 	__NETDEV_A_STATS_MAX,
 	NETDEV_A_STATS_MAX = (__NETDEV_A_STATS_MAX - 1)
-- 
2.43.2