From patchwork Thu Feb 14 21:51:01 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: bonding inactive slaves vs rx_dropped Date: Thu, 14 Feb 2013 11:51:01 -0000 From: Jay Vosburgh X-Patchwork-Id: 220525 Message-Id: <4606.1360878661@death.nxdomain> To: David Miller Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com, andy@greyhouse.net David Miller wrote: >People are starting to notice that rx_dropped now increments on every >packet received on an bond's inactive slave. > >I'm actually fine with rx_dropped incrementing in this situation. > >The problem I want to address is that rx_dropped is encompassing >several unrelated situations and thus has become less useful for >diagnosis. > >I think we should add some new RX stats such that we can get at >least a small amount of granularity for rx_dropped. > >This way team, bond, etc. can increment a new netdev_stats->rx_foo in >this situation, and then someone doing diagnosis can see that >rx_dropped and rx_foo are incrementing at similar rates. This drop isn't really happening in bonding, though. From looking at the code, it comes about because, for the inactive slave, the rx_handler call returns EXACT, and there aren't any exact match ptype bindings, so __netif_receive_skb throws it away. This isn't always the case; sometimes there is an exact match, for things like iSCSI or FCoE that are really determined to get the packet. On a non-bonded interface, the same drop path (except for the rx_handler) is taken for incoming packets for an unsupported protocol. We could probably add an, oh, rx_dropped_inactive, or some variation on that theme, that is incremented at the end of __netif_receive_skb if deliver_exact is set, e.g., something like: I think this would only hit frames that have been soft-rejected (rx_handler says EXACT) by bonding or team, but were not subsequently delivered to an exact match listener. There's the separate questions of whether there should be more counters (e.g., drops in dev_skb_forward or enqueue_to_backlog), and how to deliver the counter(s) to user space. -J --- -Jay Vosburgh, IBM Linux Technology Center, fubar@us.ibm.com -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/net/core/dev.c b/net/core/dev.c index a87bc74..4cd7c1f 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3559,6 +3559,8 @@ ncls: } else { drop: atomic_long_inc(&skb->dev->rx_dropped); + if (deliver_exact) + atomic_long_inc(&skb->dev->rx_dropped_inactive); kfree_skb(skb); /* Jamal, now you will not able to escape explaining * me how you were going to use this. :-)