From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 4F24BA04B5; Fri, 8 Nov 2019 14:31:04 +0100 (CET) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id CF9811C1AC; Fri, 8 Nov 2019 14:31:02 +0100 (CET) Received: from new2-smtp.messagingengine.com (new2-smtp.messagingengine.com [66.111.4.224]) by dpdk.org (Postfix) with ESMTP id 134FD1B19 for ; Fri, 8 Nov 2019 14:31:01 +0100 (CET) Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailnew.nyi.internal (Postfix) with ESMTP id A4BAC74E1; Fri, 8 Nov 2019 08:31:00 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute1.internal (MEProxy); Fri, 08 Nov 2019 08:31:00 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=monjalon.net; h= from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding:content-type; s=mesmtp; bh=BpNYJiPYeXeg5Lfrebo1JjIWzfMIgjQboCSJY0yjGZg=; b=a4kSO2RhqVor n62px9S2HNAq2HjibMR5EjY8ILdwhaTcAOjJQQ5t8VFY5NUazkU++cIf2CgMXcuT IvRHUReOepqddgTwtFdI7eACe+GUD2ZbjXzRWX++/SC6ESVkZFhb8tGXEKhddVWD sXfMhx56jcljQvzcyM6Z+p0PYzbhUZs= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm1; bh=BpNYJiPYeXeg5Lfrebo1JjIWzfMIgjQboCSJY0yjG Zg=; b=iOQpC90cbNGS7cXMd17Bd8okE2R+dJR6EqhfCezVsh+o58SuBwckwOxKK j1Nqt9Qm/HiAT0eL2bRHbDLWv55DBWN7KTS745zIZZxZ+1FTAaBjobcvEWS69Tqg G8V1tVSkfcYyskdTV5hWQuY8gaEhN5VhL9Q9cYMK5XhGO1WndNaPPeEsPAfXsQvc rfN6DXlnnsQfr4wad72dBCFZ9sZ+FDHcDE8m5K9s7tN5HEI6c1/NA6jioKRZ/Qa5 MzR2uzJ5xvTad97Qz5pij/YtxtM+1N51iNwYqUPVX6kzNqehRFNKcPZhC2H9HWHe nJ3Xk63DlfrKlYyAuFtCWuCKagrrw== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedufedruddvuddgheegucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhephffvufffkfgjfhgggfgtsehtufertddttddvnecuhfhrohhmpefvhhhomhgr shcuofhonhhjrghlohhnuceothhhohhmrghssehmohhnjhgrlhhonhdrnhgvtheqnecukf hppeejjedrudefgedrvddtfedrudekgeenucfrrghrrghmpehmrghilhhfrhhomhepthhh ohhmrghssehmohhnjhgrlhhonhdrnhgvthenucevlhhushhtvghrufhiiigvpedt X-ME-Proxy: Received: from xps.localnet (184.203.134.77.rev.sfr.net [77.134.203.184]) by mail.messagingengine.com (Postfix) with ESMTPA id 4733B80059; Fri, 8 Nov 2019 08:30:58 -0500 (EST) From: Thomas Monjalon To: Andrew Rybchenko Cc: Ori Kam , "dev@dpdk.org" , "pbhagavatula@marvell.com" , "ferruh.yigit@intel.com" , "jerinj@marvell.com" , John McNamara , Marko Kovacevic , Adrien Mazarguil , "david.marchand@redhat.com" , "ktraynor@redhat.com" , Olivier Matz , Raslan Darawsheh Date: Fri, 08 Nov 2019 14:30:57 +0100 Message-ID: <2760933.8gZJoIoSqR@xps> In-Reply-To: <07223bd4-da60-5c22-d9be-8f47d56c2605@solarflare.com> References: <20191025152142.12887-1-pbhagavatula@marvell.com> <1905522.nrmIJexB1b@xps> <07223bd4-da60-5c22-d9be-8f47d56c2605@solarflare.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Subject: Re: [dpdk-dev] [PATCH 1/2] ethdev: add flow action type update as an offload X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" 08/11/2019 14:27, Andrew Rybchenko: > On 11/8/19 4:17 PM, Thomas Monjalon wrote: > > 08/11/2019 13:00, Andrew Rybchenko: > >> On 11/8/19 2:03 PM, Thomas Monjalon wrote: > >>> 08/11/2019 11:42, Andrew Rybchenko: > >>>> On 11/8/19 1:28 PM, Thomas Monjalon wrote: > >>>>> 08/11/2019 09:35, Andrew Rybchenko: > >>>>>> The problem: > >>>>>> ~~~~~~~~~~~~ > >>>>>> PMD wants to know before port start if application wants to > >>>>>> to use flow MARK/FLAG in the future. It is required because: > >>>>>> > >>>>>> 1. HW may be configured in a different way to reserve resources > >>>>>> for MARK/FLAG delivery > >>>>>> > >>>>>> 2. Datapath implementation choice may depend on it (e.g. vPMD > >>>>>> is faster, but does not support MARK) > >>>>> Thank you for the clear problem statement. > >>>>> I agree with it. This is a real design issue. > >>>>> > >>>>> > >>>>>> Discussed solutions: > >>>>>> ~~~~~~~~~~~~~~~~~~~~ > >>>> May be it is not 100% clear since below are alternatives. > >>>> > >>>>>> A. Explicit Rx offload suggested by the patch. > >>>>>> > >>>>>> B. Implicit by validation of a flow rule with MARK/FLAG actions used. > >>>>>> > >>>>>> C. Use dynamic field/flag (i.e. application registers dynamic field > >>>>>> and/or flag and PMD uses lookup to solve the problem) plus part > >>>>>> of (B) to discover if a feature is supported. > >>>>> The dynamic field should be registered via a new API function > >>>>> named '_init'. > >>>>> It means the application must explicit request the feature. > >>>>> I agree this is the way to go. > >>>> If I understand your statement correctly, but (C) is not ideal since it > >>>> looks global. If registered dynamic field of mbuf and is flag that > >>>> the feature should be enabled, it is a flag to all ports/devices. > >>>> > >>>>>> All solutions require changes in applications which use these > >>>>>> features. There is a deprecation notice in place which advertises > >>>>>> DEV_RX_OFFLOAD_FLOW_MARK addition, but may be it is OK to substitute > >>>>>> it with solution (B) or (C). Solution (C) requires changes since > >>>>>> it should be combined with (B) in order to understand if > >>>>>> the feature is supported. > >>>>> I don't understand. > >>>>> Application request and PMD support are two different things. > >>>>> PMD support must be via rte_flow validation on a case by case anyway. > >>>> I mean that application wants to understand if the feature is > >>>> supported. Then, it wants to enable it. In the case of (B), > >>>> if I understand the solution correctly, there is no explicit > >>>> way to enable, PMD just detects it because of discovery is done > >>>> (that's what I mean by "implicit" and it is a drawback from my > >>>> point of view, but still could be considered). (C) solves the > >>>> problem of (B). > >>>> > >>>>>> Advantages and drawbacks of solutions: > >>>>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > >>>>>> 1. The main drawback of (A) is a "duplication" since we already > >>>>>> have a way to request flow MARK using rte_flow API. > >>>>>> I don't fully agree that it is a duplication, but I agree > >>>>>> that it sounds like duplication and complicates a bit flow > >>>>>> MARK usage by applications. (B) complicates it as well. > >>>>>> > >>>>>> 2. One more drawback of the solution (A) is the necessity of > >>>>>> similar solution for META and it eats one more offload bit. > >>>>>> Yes, that's true and I think it is not a problem. > >>>>>> It would make it easier for applications to find out if > >>>>>> either MARK or META is supported. > >>>>>> > >>>>>> 3. The main advantage of the solution (A) is simplicity. > >>>>>> It is simple for application to understand if it supported. > >>>>>> It is simple in PMD to understand that it is required. > >>>>>> It is simple to disable it - just reconfigure. > >>>>>> Also it is easier to document it - just mention that > >>>>>> the offload should be supported and enabled. > >>>>>> > >>>>>> 4. The main advantage of the solution (B) is no "duplication". > >>>>>> I agree that it is valid argument. Solving the problem > >>>>>> without extra entities is always nice, but unfortunately > >>>>>> it is too complex in this case. > >>>>>> > >>>>>> 5. The main drawback of the solution (B) is the complexity. > >>>>>> It is necessary to choose a flow rule which should be used > >>>>>> as a criteria. It could be hardware dependent. > >>>>>> Complex logic is require in PMD if it wants to address the > >>>>>> problem and control MARK delivery based on validated flow > >>>>>> rules. It adds dependency between start/stop processing and > >>>>>> flow rules validation code. > >>>>>> It is pretty complicated to document it. > >>>>>> > >>>>>> 6. Useless enabling of the offload in the case of solution (A) > >>>>>> if really used flow rules do not support MARK looks like > >>>>>> drawback as well, but easily mitigated by a combination > >>>>>> with solution (B) and only required if the application wants > >>>>>> to dive in the level of optimization and complexity and > >>>>>> makes sense if application knows required flow rules in > >>>>>> advance. So, it is not a problem in this case. > >>>>>> > >>>>>> 7. Solution (C) has drawbacks of the solution (B) for > >>>>>> applications to understand if these features are supported, > >>>>>> but no drawbacks in PMD, since explicit criteria is used to > >>>>>> enable/disable (dynamic field/flag lookup). > >>>>>> > >>>>>> 8. Solution (C) is nice since it avoids "duplication". > >>>>>> > >>>>>> 9. The main drawback of the solution (C) is asymmetry. > >>>>>> As it was discussed in the case of RX_TIMESTAMP > >>>>>> (if I remember it correctly): > >>>>>> - PMD advertises RX_TIMESTAMP offload capability > >>>>>> - application enables the offload > >>>>>> - PMD registers dynamic field for timestamp > >>>>>> Solution (C): > >>>>>> - PMD advertises nothing > >>>>>> - application uses solution (B) to understand if > >>>>>> these features are supported > >>>>>> - application registers dynamic field/flag > >>>>>> - PMD does lookup and solve the problem > >>>>>> The asymmetry could be partially mitigated if RX_TIMESTAMP > >>>>>> solution is changed to require an application to register > >>>>>> dynamic fields and PMD to do lookup if the offload is > >>>>>> enabled. So, the only difference will be in no offload > >>>>>> in the case of flow MARK/FLAG and usage of complex logic > >>>>>> to understand if it is supported or no. > >>>>>> May be it would be really good since it will allow to > >>>>>> have dynamic fields registered before mempool population. > >>>>>> > >>>>>> 10. Common drawback of solutions (B) and (C) is no granularity. > >>>>>> Solution (A) may be per queue while (B) and (C) cannot be > >>>>>> per queue. Moreover (C) looks global - for all devices. > >>>>>> It could be really painful. > >>>>>> > >>>>>> (C) is nice, but I still vote for simplicity and > >>>>>> granularity of (A). > >>>>> I vote for clear separation of application needs and PMD support, > >>>>> by using the method C (dynamic fields). > >>>>> I agree timestamp must use the same path. > >>>>> I agree it's complicate because we don't know in advance whether > >>>>> a flow rule will be accepted, but that's the reality, config is complex. > >>>> Do you think that global nature of the (C) is acceptable? > >>> That's a good question. > >>> Maybe the feature request should be per port. > >>> In this case, we are back to solution A with a flag per port? > >> Offloads are natively per-queue as well, so (A) keeps the choice > >> between per-port vs per-queue to PMDs as usual. > >> > >>> Note that A and C will not guarantee that the offload will be possible. > >> Yes, definitely. > >> > >>> We need B (flow rule validation) anyway. > >> Strictly speaking (B) (checking flow rules before device > >> startup) is required if an application can predict flow > >> rules and wants to ensure that MARK offload will be usable. > >> Otherwise, it may be skipped. > > No no, I mean flow rule validation MUST be used anyway > > during the runtime before applying a rule. > > I agree it is hard to predict. I speak only about real rules. > > OK, I see. Of course, flow rule validation is required at runtime. > I was rather concentrated on the stated problem solutions. > > >>> It seems A, B, C are not alternatives but all required > >>> as pieces of a puzzle... > >> Unfortunately true in the most complex case. > >> Right now it will be A with B if required as explained above. > >> C will come a bit later when the field migrates to dynamic. > >> > >> May be it is even better if application registers dynamic > >> fields before an attempt to enable offload to be sure that > >> it will not fail because of impossibility to register > >> dynamic field (lack of space). I'm not sure, but it is not > >> not that important. > > Yes of course, lack of mbuf space is another reason for > > disabling the feature. > > > >> If we finally go way A, should we add offloads for META back? > >> I guess separate Rx and Tx are required. > > I would prefer to add it as dynamic flags. > > Why rushing on a very temporary solution while it is not a new issue? > > Basically it means that we go just (B)+(C) in the case of META. > I have no strong opinion but thought that it could be better to > align the solution. Of course, we can wait with it. As I understand > META is an experimental feature. Yes it is experimental and I think it is too late to align now. Anyway, we will probably to discuss again these offloads TAG/MARK/META, as requested by several people.