[RFC net-next v3 0/2] mlx5: Add netdev-genl queue stats

[Joe Damato <jdamato@fastly.com>]

Greetings:

Switching to an RFC instead of a PATCH because even though Tariq
patiently explained the code to me, I'm sure I probably still missed
something ;)

If this turns out to be right and Tariq agrees, I can send a PATCH
net-next v4.

This change adds support for the per queue netdev-genl API to mlx5,
which seems to output stats:

./cli.py --spec ../../../Documentation/netlink/specs/netdev.yaml \
         --dump qstats-get --json '{"scope": "queue"}'

...snip
 {'ifindex': 7,
  'queue-id': 28,
  'queue-type': 'tx',
  'tx-bytes': 399462,
  'tx-packets': 3311},
...snip

I've used the suggested tooling to verify the per queue stats match
rtnl by doing this:

  NETIF=eth0 tools/testing/selftests/drivers/net/stats.py

I've tested the following scenarios:
  - The machine at boot (default queue configuration)
  - Adjusting the queue configuration to various amounts via ethtool
  - Add mqprio TCs
  - Removing the mqprio TCs

and in each scenario the stats script above reports that the stats match
rtnl.

Worth noting that Tariq suggested I also export HTB/QOS stats in
mlx5e_get_base_stats.

I am open to doing this, but I think if I were to do that, HTB/QOS queue
stats should also be exported by rtnl so that the script above will
continue to show that the output is correct.

I'd like to propose: adding HTB/QOS to both rtnl *and* the netdev-genl
code together at the same time, but a later time, separate from this
change.

Thanks,
Joe

v2 -> rfcv3:
 - Added patch 1/2 which creates some helpers for computing the txq_ix
   and ch_ix/tc_ix.

 - Patch 2/2 modified in several ways:
   - Fixed variable declarations in mlx5e_get_queue_stats_rx to be at
     the start of the function.
   - mlx5e_get_queue_stats_tx rewritten to access sq stats directly by
     using the helpers added in the previous patch.
   - mlx5e_get_base_stats modified in several ways:
     - Took the state_lock when accessing priv->channels.
     - For the base RX stats, code was simplified to call
       mlx5e_get_queue_stats_rx instead of repeating the same code.
     - For the base TX stats, I attempted to implement what I think
       Tariq suggested in the previous thread:
         - for available channels, only unavailable TC stats are summed
	 - for unavailable channels, all stats for TCs up to
	   max_opened_tc are summed.

v1 - > v2:
  - Essentially a full rewrite after comments from Jakub, Tariq, and
    Zhu.

Joe Damato (2):
  net/mlx5e: Add helpers to calculate txq and ch idx
  net/mlx5e: Add per queue netdev-genl stats

 .../net/ethernet/mellanox/mlx5/core/en_main.c | 150 +++++++++++++++++-
 1 file changed, 149 insertions(+), 1 deletion(-)

-- 
2.25.1