On Thu, 31 Jan 2019 08:31:51 -0800, Roopa Prabhu wrote:

On Thu, Jan 31, 2019 at 8:16 AM Roopa Prabhu wrote:

quoted

On Wed, Jan 30, 2019 at 4:24 PM Jakub Kicinski wrote:  

quoted

On Wed, 30 Jan 2019 14:14:34 -0800, Roopa Prabhu wrote:  

My thinking was that we should leave truly custom/strange stats to
ethtool API which works quite well for that and at the same time be
very accepting of people adding new IDs to HSTAT (only requirement is
basically defining the meaning very clearly).  

that sounds reasonable. But the 'defining meaning clearly' gets tricky
sometimes.
The vendor who gets their ID or meaning first wins :) and the rest
will have to live with
ethtool and explain to rest of the world that ethtool is more reliable
for their hardware :)

Right, that's the trade off inherent to standardization.  I don't see
any way to work around the fact that the definition may not fit all.

What I want as a end user and what I want for my customers is the
ability to switch the NIC on their system and not spend two months
"integrating" into their automation :(  If the definition of statistics
is not solid we're back to square one.

quoted

I am also concerned that this getting the ID into common HSTAT ID
space will  slow down the process of adding new counters
for vendors. Which will lead to vendors sticking with ethtool API. 

I feel like whatever we did here will end up looking much like the
ethtool interface, which is why I decided to leave that part out.
Ethtool -S works pretty well for custom stats.  Standard and structured
stats don't fit with it in any way, the two seem best left separate.

quoted

It would be great if people can get all stats in one place and not
rely on another API for 'more'.

One place in the driver or for the user?  I'm happy to add the code to
ethtool to also dump hstats and render them in a standard way.  In fact
the tool I have for testing has a "simplified" output format which
looks exactly like ethtool -S.

One place for the driver to report is hard, as I said I think the
custom stats are best left with ethtool.  Adding an extra incentive to
standardize.

quoted

quoted

For the first stab I looked at two drivers and added all the stats that
were common.

Given this set is identifying statistics by ID - how would we make that
extensible to drivers?  Would we go back to strings or have some
"driver specific" ID space?  

I was looking for ideas from you really, to see if you had considered
this. agree per driver ID space seems ugly.
ethtool strings are great today...if we can control the duplication.
But thinking some more..., i did see some
patches recently for vendor specific parameter (with ID) space in
devlink. maybe something like that will be
reasonable ?

I thought about this for a year and I basically came to the conclusion
I can't find any perfect solution, if there is one.

The devlink parameters are useful, but as anticipated they became the
laziest excuse of an ABI... Don't get me started ;)

quoted

quoted

Is there any particular type of statistic you'd expect drivers to want
to add?  For NICs I think IEEE/RMON should pretty much cover the
silicon ones, but I don't know much about switches :)  

I will have to go through the list. But switch asics do support
flexible stats/counters that can be attached at various points.
And new chip versions come with more support. Having that flexibility
to expose/extend such stats incrementally is very valuable on a per
hardware/vendor basis.  

Yes, I'm not too familiar with those counters.  Do they need to be
enabled to start counting?  Do they have performance impact?  Can the
"sample" events perf-style?  How is the condition on which they trigger
defined?  Is it maybe just "match a packet and increment a counter"?
Would such counters benefit from hierarchical structure?

I was trying to cover the long standing use cases - namely the
IEEE/RMON stats which all MAC have had for years and per queue stats
which all drivers have had for years.  But if we can cater to more
cases I'm open.

Just want to clarify that I am suggesting a nested HSTATS extension
infra for drivers (just like ethtool).
'Common stats' stays at the top-level.

I got a concept of groups here.  The dump generally looks like this:

[root group A (say MAC stats)]
  [sub group RX]
  [sub group TX]
[root group B (say PCIe stats)]
  [sub group RX]
  [sub group TX]
[root group C (say per-q driver stats]
  [sub group RX]
    [q1 group]
    [q2 group]
    [q3 group]
  [sub group TX]
    [q1 group]
    [q2 group]
    [q3 group]

Each root group representing a "point in the pipeline".

So it's not too hard to add a root group with whatever, the questions
are move how would it benefit over existing ethtool if the stats are
custom anyway?  Hm..