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From: Adrien Mazarguil <adrien.mazarguil@6wind.com>
To: Yongseok Koh <yskoh@mellanox.com>
Cc: Shahaf Shuler <shahafs@mellanox.com>,
	Thomas Monjalon <thomas@monjalon.net>,
	Ferruh Yigit <ferruh.yigit@intel.com>,
	Andrew Rybchenko <arybchenko@solarflare.com>,
	Olivier Matz <olivier.matz@6wind.com>, dev <dev@dpdk.org>,
	Slava Ovsiienko <viacheslavo@mellanox.com>
Subject: Re: [dpdk-dev] [PATCH] ethdev: add flow tag
Date: Tue, 9 Jul 2019 10:38:06 +0200	[thread overview]
Message-ID: <20190709083806.GS4512@6wind.com> (raw)
In-Reply-To: <6EE319CD-4BBC-47BF-AAE5-2165B8C1D491@mellanox.com>

On Fri, Jul 05, 2019 at 06:05:50PM +0000, Yongseok Koh wrote:
> > On Jul 5, 2019, at 6:54 AM, Adrien Mazarguil <adrien.mazarguil@6wind.com> wrote:
> > 
> > On Thu, Jul 04, 2019 at 04:23:02PM -0700, Yongseok Koh wrote:
> >> A tag is a transient data which can be used during flow match. This can be
> >> used to store match result from a previous table so that the same pattern
> >> need not be matched again on the next table. Even if outer header is
> >> decapsulated on the previous match, the match result can be kept.
> >> 
> >> Some device expose internal registers of its flow processing pipeline and
> >> those registers are quite useful for stateful connection tracking as it
> >> keeps status of flow matching. Multiple tags are supported by specifying
> >> index.
> >> 
> >> Example testpmd commands are:
> >> 
> >>  flow create 0 ingress pattern ... / end
> >>    actions set_tag index 2 value 0xaa00bb mask 0xffff00ff /
> >>            set_tag index 3 value 0x123456 mask 0xffffff /
> >>            vxlan_decap / jump group 1 / end
> >> 
> >>  flow create 0 ingress pattern ... / end
> >>    actions set_tag index 2 value 0xcc00 mask 0xff00 /
> >>            set_tag index 3 value 0x123456 mask 0xffffff /
> >>            vxlan_decap / jump group 1 / end
> >> 
> >>  flow create 0 ingress group 1
> >>    pattern tag index is 2 value spec 0xaa00bb value mask 0xffff00ff /
> >>            eth ... / end
> >>    actions ... jump group 2 / end
> >> 
> >>  flow create 0 ingress group 1
> >>    pattern tag index is 2 value spec 0xcc00 value mask 0xff00 /
> >>            tag index is 3 value spec 0x123456 value mask 0xffffff /
> >>            eth ... / end
> >>    actions ... / end
> >> 
> >>  flow create 0 ingress group 2
> >>    pattern tag index is 3 value spec 0x123456 value mask 0xffffff /
> >>            eth ... / end
> >>    actions ... / end
> >> 
> >> Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
> > 
> > Hi Yongseok,
> > 
> > Only high level questions for now, while it unquestionably looks useful,
> > from a user standpoint exposing the separate index seems redundant and not
> > necessarily convenient. Using the following example to illustrate:
> > 
> > actions set_tag index 3 value 0x123456 mask 0xfffff
> > 
> > pattern tag index is 3 value spec 0x123456 value mask 0xffffff
> > 
> > I might be missing something, but why isn't this enough:
> > 
> > pattern tag index is 3 # match whatever is stored at index 3
> > 
> > Assuming it can work, then why bother with providing value spec/mask on
> > set_tag? A flow rule pattern matches something, sets some arbitrary tag to
> > be matched by a subsequent flow rule and that's it. It even seems like
> > relying on the index only on both occasions is enough for identification.
> > 
> > Same question for the opposite approach; relying on the value, never
> > mentioning the index.
> > 
> > I'm under the impression that the index is a hardware-specific constraint
> > that shouldn't be exposed (especially since it's an 8-bit field). If so, a
> > PMD could keep track of used indices without having them exposed through the
> > public API.
> 
> 
> Thank you for review, Adrien.
> Hope you are doing well. It's been long since we talked each other. :-)

Yeah clearly! Hope you're doing well too. I'm somewhat busy hence slow to
answer these days...

 <dev@dpdk.org> hey!
 <dev@dpdk.org> no private talks!

Back to the topic:

> Your approach will work too in general but we have a request from customer that
> they want to partition this limited tag storage. Assuming that HW exposes 32bit
> tags (those are 'registers' in HW pipeline in mlx5 HW). Then, customers want to
> store multiple data even in a 32-bit storage. For example, 16bit vlan tag, 8bit
> table id and 8bit flow id. As they want to split one 32bit storage, I thought it
> is better to provide mask when setting/matching the value. Even some customer
> wants to store multiple flags bit by bit like ol_flags. They do want to alter
> only partial bits.
> 
> And for the index, it is to reference an entry of tags array as HW can provide
> larger registers than 32-bit. For example, mlx5 HW would provide 4 of 32b
> storage which users can use for their own sake.
> 	tag[0], tag[1], tag[2], tag[3]

OK, looks like I missed the point then. I initially took it for a funky
alternative to RTE_FLOW_ITEM_TYPE_META & RTE_FLOW_ACTION_TYPE_SET_META
(ingress extended [1]) but while it could be used like that, it's more of a
way to temporarily store and retrieve a small amount of data, correct?

Out of curiosity, are these registers independent from META and other
items/actions in mlx5, otherwise what happens if they are combined?

Are there other uses for these registers? Say, referencing their contents
from other places in a flow rule so they don't have to be hard-coded?

Right now I'm still uncomfortable with such a feature in the public API
because compared to META [1], this approach looks very hardware-specific and
seemingly difficult to map on different HW architectures.

However, the main problem is that as described, its end purpose seems
redundant with META, which I think can cover the use cases you gave. So what
can an application do with this that couldn't be done in a more generic
fashion through META?

I may still be missing something and I'm open to ideas, but assuming it
doesn't make it into the public rte_flow API, it remains an interesting
feature on its own merit which could be added to DPDK as PMD-specific
pattern items/actions [2]. mlx5 doesn't have any yet, but it's pretty common
for PMDs to expose a public header that dedicated applications can include
to use this kind of features (look for rte_pmd_*.h, e.g. rte_pmd_ixgbe.h).
No problem with that.

[1] "[PATCH] ethdev: extend flow metadata"
    https://mails.dpdk.org/archives/dev/2019-July/137305.html

[2] "Negative types"
    https://doc.dpdk.org/guides/prog_guide/rte_flow.html#negative-types

-- 
Adrien Mazarguil
6WIND

  parent reply	other threads:[~2019-07-09  8:38 UTC|newest]

Thread overview: 98+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-03 21:32 [dpdk-dev] [RFC 1/3] ethdev: extend flow metadata Yongseok Koh
2019-06-03 21:32 ` [dpdk-dev] [RFC 2/3] ethdev: add flow modify mark action Yongseok Koh
2019-06-06 10:35   ` Jerin Jacob Kollanukkaran
2019-06-06 18:33     ` Yongseok Koh
2019-06-03 21:32 ` [dpdk-dev] [RFC 3/3] ethdev: add flow tag Yongseok Koh
2019-07-04 23:23   ` [dpdk-dev] [PATCH] " Yongseok Koh
2019-07-05 13:54     ` Adrien Mazarguil
2019-07-05 18:05       ` Yongseok Koh
2019-07-08 23:32         ` Yongseok Koh
2019-07-09  8:38         ` Adrien Mazarguil [this message]
2019-07-11  1:59           ` Yongseok Koh
2019-10-08 12:57             ` Yigit, Ferruh
2019-10-08 13:18               ` Slava Ovsiienko
2019-10-10 16:09     ` [dpdk-dev] [PATCH v2] " Viacheslav Ovsiienko
2019-10-24 13:12       ` [dpdk-dev] [PATCH v3] " Viacheslav Ovsiienko
2019-10-27 16:38         ` Ori Kam
2019-10-27 18:42         ` [dpdk-dev] [PATCH v4] " Viacheslav Ovsiienko
2019-10-27 19:11           ` Ori Kam
2019-10-31 18:57             ` Ferruh Yigit
2019-06-09 14:23 ` [dpdk-dev] [RFC 1/3] ethdev: extend flow metadata Andrew Rybchenko
2019-06-10  3:19   ` Wang, Haiyue
2019-06-10  7:20     ` Andrew Rybchenko
2019-06-11  0:06       ` Yongseok Koh
2019-06-19  9:05         ` Andrew Rybchenko
2019-07-04 23:21 ` [dpdk-dev] [PATCH] " Yongseok Koh
2019-07-10  9:31   ` Olivier Matz
2019-07-10  9:55     ` Bruce Richardson
2019-07-10 10:07       ` Olivier Matz
2019-07-10 12:01         ` Bruce Richardson
2019-07-10 12:26           ` Thomas Monjalon
2019-07-10 16:37             ` Yongseok Koh
2019-07-11  7:44               ` Adrien Mazarguil
2019-07-14 11:46                 ` Andrew Rybchenko
2019-07-29 15:06                   ` Adrien Mazarguil
2019-10-08 12:51                     ` Yigit, Ferruh
2019-10-08 13:17                       ` Slava Ovsiienko
2019-10-10 16:02   ` [dpdk-dev] [PATCH v2] " Viacheslav Ovsiienko
2019-10-18  9:22     ` Olivier Matz
2019-10-19 19:47       ` Slava Ovsiienko
2019-10-21 16:37         ` Olivier Matz
2019-10-24  6:49           ` Slava Ovsiienko
2019-10-24  9:22             ` Olivier Matz
2019-10-24 12:30               ` Slava Ovsiienko
2019-10-24 13:08     ` [dpdk-dev] [PATCH v3] " Viacheslav Ovsiienko
2019-10-27 16:56       ` Ori Kam
2019-10-27 18:40       ` [dpdk-dev] [PATCH v4] " Viacheslav Ovsiienko
2019-10-27 19:10         ` Ori Kam
2019-10-29 16:22         ` Andrew Rybchenko
2019-10-29 17:19           ` Slava Ovsiienko
2019-10-29 18:30             ` Thomas Monjalon
2019-10-29 18:35               ` Slava Ovsiienko
2019-10-30  6:28               ` Andrew Rybchenko
2019-10-30  7:35             ` Andrew Rybchenko
2019-10-30  8:59               ` Slava Ovsiienko
2019-10-30  9:20                 ` Andrew Rybchenko
2019-10-30 10:05                   ` Slava Ovsiienko
2019-10-30 10:03                 ` Slava Ovsiienko
2019-10-30 15:49               ` Olivier Matz
2019-10-31  9:25                 ` Andrew Rybchenko
2019-10-29 16:25         ` Olivier Matz
2019-10-29 16:33           ` Olivier Matz
2019-10-29 17:53             ` Slava Ovsiienko
2019-10-29 17:43           ` Slava Ovsiienko
2019-10-29 19:31         ` [dpdk-dev] [PATCH v5] " Viacheslav Ovsiienko
2019-10-30  8:02           ` Andrew Rybchenko
2019-10-30 14:40             ` Slava Ovsiienko
2019-10-30 14:46               ` Slava Ovsiienko
2019-10-30 15:20                 ` Olivier Matz
2019-10-30 15:57                   ` Thomas Monjalon
2019-10-30 15:58                   ` Slava Ovsiienko
2019-10-30 16:13                     ` Olivier Matz
2019-10-30  8:35           ` Ori Kam
2019-10-30 17:12           ` [dpdk-dev] [PATCH v6 0/2] extend flow metadata feature Viacheslav Ovsiienko
2019-10-30 17:12             ` [dpdk-dev] [PATCH v6 1/2] ethdev: extend flow metadata Viacheslav Ovsiienko
2019-10-31  9:19               ` Andrew Rybchenko
2019-10-31 13:05               ` [dpdk-dev] [PATCH v7 0/2] extend flow metadata feature Viacheslav Ovsiienko
2019-10-31 13:05                 ` [dpdk-dev] [PATCH v7 1/2] ethdev: extend flow metadata Viacheslav Ovsiienko
2019-10-31 15:47                   ` Olivier Matz
2019-10-31 16:13                     ` Slava Ovsiienko
2019-10-31 16:48                   ` [dpdk-dev] [PATCH v8 0/2] extend flow metadata feature Viacheslav Ovsiienko
2019-10-31 16:48                     ` [dpdk-dev] [PATCH v8 1/2] ethdev: extend flow metadata Viacheslav Ovsiienko
2019-11-04  6:13                       ` [dpdk-dev] [PATCH v9 0/2] extend flow metadata feature Viacheslav Ovsiienko
2019-11-04  6:13                         ` [dpdk-dev] [PATCH v9 1/2] ethdev: extend flow metadata Viacheslav Ovsiienko
2019-11-05 14:19                           ` [dpdk-dev] [PATCH v10 0/2] extend flow metadata feature Viacheslav Ovsiienko
2019-11-05 14:19                             ` [dpdk-dev] [PATCH v10 1/2] ethdev: extend flow metadata Viacheslav Ovsiienko
2019-11-05 14:19                             ` [dpdk-dev] [PATCH v10 2/2] ethdev: move egress metadata to dynamic field Viacheslav Ovsiienko
2019-11-06 15:49                             ` [dpdk-dev] [PATCH v10 0/2] extend flow metadata feature Ferruh Yigit
2019-11-04  6:13                         ` [dpdk-dev] [PATCH v9 2/2] ethdev: move egress metadata to dynamic field Viacheslav Ovsiienko
2019-10-31 16:48                     ` [dpdk-dev] [PATCH v8 " Viacheslav Ovsiienko
2019-10-31 17:21                       ` Olivier Matz
2019-11-01 12:34                       ` Andrew Rybchenko
2019-10-31 13:05                 ` [dpdk-dev] [PATCH v7 " Viacheslav Ovsiienko
2019-10-31 13:33                   ` Ori Kam
2019-10-31 15:51                   ` Olivier Matz
2019-10-31 16:07                     ` Slava Ovsiienko
2019-10-30 17:12             ` [dpdk-dev] [PATCH v6 " Viacheslav Ovsiienko
2019-10-31  9:01               ` Andrew Rybchenko
2019-10-31 10:54                 ` Slava Ovsiienko

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