On 2/1/23 13:58, Thomas Monjalon wrote:
01/02/2023 11:17, Andrew Rybchenko:
On 1/18/23 19:18, Thomas Monjalon wrote:
18/01/2023 08:28, Andrew Rybchenko:
On 11/14/22 14:59, Rongwei Liu wrote:
In case flow rules match only one kind of traffic in a flow table,
then optimization can be done via allocation of this table.
Such optimization is possible only if the application gives a hint
about its usage of the table during initial configuration.
The transfer domain rules may process traffic from wire or vport,
which may correspond to two kinds of underlayer resources.
That's why the first two hints introduced in this patch are about
wire and vport traffic specialization.
Wire means traffic arrives from the uplink port while vport means
traffic initiated from VF/SF.
There are two possible approaches for providing the hints.
Using IPv4 as an example:
1. Use pattern item in both template table and flow rules.
pattern_template: pattern ANY_VPORT / eth / ipv4 is 1.1.1.1 / end
async flow create: pattern ANY_VPORT / eth / ipv4 is 1.1.1.2 / end
"ANY_VPORT" needs to be present in each flow rule even if it's
just a hint. No value to match because matching is already done by
IPv4 item.
2. Add special flags into table_attr.
template_table 0 create table_id 0 group 1 transfer vport_orig
Approach 1 needs to specify the pattern in each flow rule which wastes
memory and is not user friendly.
This patch takes the 2nd approach and introduces one new member
"specialize" into rte_flow_table_attr to indicate possible flow table
optimization.
The above description is misleading. It alternates options (1)
and (2), but in fact (2) requires (1) as well.
Yes the above description may be misleading
and it seems you are misleaded :)
It is not my intention. If it is only my problem, I'm OK to
step back.
It's OK to explain and check everything is OK, no worries.
Thanks for reviewing.
I will explain below why the option (2) doesn't require (1).
I think we should apply the same example to both cases to make it clear:
1. Use pattern item in both template table and flow rules:
template table 3 = transfer pattern ANY_VPORT / eth / ipv4 src is
255.255.255.255 / end
flow rule = template_table 3 pattern ANY_VPORT / eth / ipv4 src is 1.1.1.1
/ end
The pattern template 3 will be used only to match flows coming from vports.
ANY_VPORT needs to be present in each flow rule.
It looks like I lost something here. Why do we need to specify
it in each flow rule if the matching is already fixed in
template table?
I think that's how template tables are designed.
Ori, please could you point us to the relevant documentation?
ANY_VPORT matching is redundant with IP src 1.1.1.1 because
the user knows 1.1.1.1 is the IP of a vport.
What should happen if a packet with src IP 1.1.1.1 comes from
the wire? Almost anything could come from network.
It a packet comes from a wired port AND
the PMD did an optimization based on this hint,
then the packet could be not matched.
So, the hint changes matching results and therefore becomes
a strange (extra) matching criteria under specific
circumstance. It sounds bad. So, good application must use
real (always) matching criteria when composing flow rules.
So, RTE flow API should provide a way to write a good
application without extra pain.
That's why I'm saying that (2) requires (1) anyway.
It does not say that hint is not required at all.
It is still useful for resources usage optimization if
application knows how it is going to use particular table.
2. Add specialization flag into template table attribute:
template table 3 = transfer VPORT_ORIG pattern eth / ipv4 src is
255.255.255.255 / end
flow rule = template_table 3 pattern eth / ipv4 src is 1.1.1.1 / end
The pattern template 3 can be used only to match flows coming from vports.
In this case it is interesting how it will behave on:
a NIC which does not support VPORT_ORIG and just ignores it
If the hint is ignored, all packets will hit the rule.
VS
a NIC which support VPORT_ORIG and takes it into account.
If the hint is taken into account,
it is possible that wire packets do not hit this rule,
but we don't really know, it is an internal driver optimization.
(2) is simply done on different level - much earlier, before
flow rules creation. Since resources allocation is assumed to
be done on table creation, we need to know the purpose of the
table in advance to optimize resources allocation.
Actually in both cases we get the hint at template table creation.
But in solution 2 we are not creating a redundant pattern matching,
and we don't need to check it in flow rules, so it is more efficient.
Since (2) is *not a matching criteria*, but just a hint, (1)
flow rules must have matching criteria anyway.
No we don't need the matching criteria ANY_VPORT with solution (2)
because we are already matching on an IP src which is a vport.
+Table Attribute: Specialize
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Application can help optimizing underlayer resources and insertion rate
+by specializing template table.
+Specialization is done by providing hints
+in the template table attribute ``specialize``.
+
+This attribute is not mandatory for each PMD to implement.
+If a hint is not supported, it will be silently ignored,
+and no special optimization is done.
+
+If a table is specialized, the application should make sure the rules
+comply with the table attribute.
If a table is specialized, the application must make sure that
all flow rules added to the table have pattern which implies
corresponding matching criteria. For example if a table is
specialized to be wire-origin only, pattern should have
represented port item with ethdev which corresponds to a
physical port (or any other item which matches packets
coming from wire only).
No need of a matching criteria strictly mapping the hint.
Here the hint is SPECIALIZE_TRANSFER_VPORT_ORIG
and the rules can match on an IP src which is assigned to a vport.
So there is no need to strictly match the vport itself in the rule.
If so, the problem is that the same rules will behave in a different way
on different NICs.
Not exactly.
If the assumption made by the application is wrong,
yes there may be some differences for the unexpected packets.
But it would be a user mistake somewhere.
In general, an application should have the same functional result,
no matter the hint is used or not by the driver.
Hope it make thinks clear.
We can improve the commit log as I wrote above.
