On 5/19/22 05:17, Alexander Kozyrev wrote:
On Wed, May 18, 2022 12:51 Andrew Rybchenko <andrew.rybche...@oktetlabs.ru>:
I'm sorry, I'm not sure that I can take part in tomorrow meeting, so,
I'd like to drop my thoughts on the topic via E-mail.
Thank you for taking some time and reviewing this RFC.
Existing "meter" object which pulls profile and policy together allows
do apply metering in one flow-based lookup for different flows.
I.e. we can route absolutely different flows to one meter object to
share metering counters. When we know meter ID for a flow, everything
becomes simple - just get corresponding metering counters, apply it and
do actions based on color. Yes, it is not flexible, but very simple. As
I understand the configuration model enforces to define actions for all
colors.
Yes, and what I propose is the flexible version of Meters where both
profiles and policies can be used separately. But flexibility comes with
a price of taking care of both of them separately as well, of course.
A new model, if I'm not mistaken, will require three flow-based lookups:
1. To assign a TAG based on flow fields (to handle different flows in
one meter)
2. To do metering for packets with a TAG
3. To find actions based on color
Of course, (2) and (3) are done in existing model with meter ID, but
here it is a generic flow-based lookups with extra matching criteria.
Yes, it is true that it gives extra flexibility, but everything has its
price.
We don't need to assign a TAG. I used the TAG as example on how we can
combine color matching with any other item matching. Model stays the same.
You still do color marking with a meter and find actions based on a color.
I general yes, but I've tried to highlight the case when the
same meter should be applied to different flows. If so, you
need a way to combine. Old way allows to do it in a single step - just
specify meter ID. New way needs extra rule, for example,
using TAG or MARK.
Theoretically old model could be expressed using new one (and,
therefore, supported on old HW), but it is a bit tricky and raises many
questions on how to handle it correctly in all cases. E.g. if a TAG is
the only pattern in non-zero table and used for meter+jump actions only,
it could be associated with meter ID.
Above jump table specified after meter action could be associated with a
policy ID. If action for a color is not specified in a table, it should
be drop by default.
Yes, old model can be expressed via new API and new model can be
simulated with the old API. Efficiency and performance is the key.
Indirect actions or action templates could help to do meter profile job
- define profile in single place.
True, meter color marking may be used for meter sharing, for example.
To sum up, since some HW could support the flexibility provided by
suggested flow API items/actions. I see no reason to block it. Solution
looks good from flow API design point of view.
Thank you.
May be I'm missing something since I'm not expert in QoS and have no
hands-on experience with meters in DPDK.
Andrew.
