netdev - Re: [PATCH net-next 2/2] mpls: Packet stats

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Message-ID: <587959DC.9020403@cumulusnetworks.com>
Date:   Fri, 13 Jan 2017 14:51:08 -0800
From:   Roopa Prabhu <roopa@...ulusnetworks.com>
To:     Robert Shearman <rshearma@...cade.com>
CC:     davem@...emloft.net, netdev@...r.kernel.org,
        David Ahern <dsa@...ulusnetworks.com>, ebiederm@...ssion.com
Subject: Re: [PATCH net-next 2/2] mpls: Packet stats

On 1/13/17, 10:14 AM, Robert Shearman wrote:
> Having MPLS packet stats is useful for observing network operation and
> for diagnosing network problems. In the absence of anything better,
> RFC2863 and RFC3813 are used for guidance for which stats to expose
> and the semantics of them. In particular rx_noroutes maps to in
> unknown protos in RFC2863. The stats are exposed to userspace via
> AF_MPLS attributes embedded in the IFLA_STATS_AF_SPEC attribute of
> RTM_GETSTATS messages.
>
> All the introduced fields are 64-bit, even error ones, to ensure no
> overflow with long uptimes. Per-CPU counters are used to avoid
> cache-line contention on the commonly used fields. The other fields
> have also been made per-CPU for code to avoid performance problems in
> error conditions on the assumption that on some platforms the cost of
> atomic operations could be more expensive than sending the packet
> (which is what would be done in the success case). If that's not the
> case, we could instead not use per-CPU counters for these fields.
>
> Only unicast and non-fragment are exposed at the moment, but other
> counters can be exposed in the future either by adding to the end of
> struct mpls_link_stats or by additional netlink attributes in the
> AF_MPLS IFLA_STATS_AF_SPEC nested attribute.
>
> Signed-off-by: Robert Shearman <rshearma@...cade.com>
> ---
>
Acked-by: Roopa Prabhu <roopa@...ulusnetworks.com>