netdev - Re: [PATCH net-next 1/2] mpls: packet stats

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Date:	Thu, 28 Jul 2016 22:19:56 -0700
From:	Roopa Prabhu <roopa@...ulusnetworks.com>
To:	Robert Shearman <rshearma@...cade.com>
CC:	davem@...emloft.net, netdev@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH net-next 1/2] mpls: packet stats

On 2/5/16, 11:27 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,
> use RFCs for MIBs defining MPLS stats for guidance on the semantics of
> the stats to expose. RFC3813 details two per-interface packet stats
> that should be provided (label lookup failures and fragmented packets)
> and also provides interpretation of RFC2863 for other per-interface
> stats (in/out ucast, mcast and bcast, in/out discards and errors and
> in unknown protos).
>
> Multicast, fragment and broadcast packet counters are printed, but not
> stored to allow for future implementation of current standards or
> future standards without user-space having to change.
>
> 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 pexpensive 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.
>
> The IPv6 proc code was used as an inspiration for the proc code
> here, both in terms of the implementation as well as the location of
> the per-device stats proc files: /proc/net/dev_snmp_mpls/<dev>.
>
> Signed-off-by: Robert Shearman <rshearma@...cade.com>
>
Robert, any interest in moving this to the new stats api ?.

I had done some work for AF_<family> stats. Did not eventually end up including it in the
final version. The AF_<family> infra patch is here:
https://github.com/CumulusNetworks/net-next/commits/mpls-stats

Thanks!.