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 2E902A04B4; Fri, 8 Nov 2019 14:17:28 +0100 (CET) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 086321C1A2; Fri, 8 Nov 2019 14:17:28 +0100 (CET) Received: from new2-smtp.messagingengine.com (new2-smtp.messagingengine.com [66.111.4.224]) by dpdk.org (Postfix) with ESMTP id 99C6E1C0B7 for ; Fri, 8 Nov 2019 14:17:26 +0100 (CET) Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailnew.nyi.internal (Postfix) with ESMTP id F06BB709C; Fri, 8 Nov 2019 08:17:25 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute1.internal (MEProxy); Fri, 08 Nov 2019 08:17:26 -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=dzKvNO0KSvmWPEwH2C7EKDTnfkTaSzJCBOsPFhVbjSE=; b=QkyZV/wLRKiI MxzRmfj8RQQM9aBnkDrrjkaVLPURGm5aiueoFmmMViQMeCxHgVoLAzWTLyU2koid hjjZ9rtKygCvHKEwBgB6tknrn75t0/ySvhh+z9qaH8/+J5fLBHxxliNIhWv4eYbT L1TShL4gbJJSDJQ5uQuP2W6bdg/qej4= 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=dzKvNO0KSvmWPEwH2C7EKDTnfkTaSzJCBOsPFhVbj SE=; b=tlp7xD+uKE6vS7lpwiY92qemmhi8uNTyD2bWgco1IQ6jxl5DcbD3vZ4iY H8A1ton+vYAhrc37+Q4K/UuA1hczx7q3AtiLJjhdFrEJrXPJkfUw7u2XY9e75PSG ZLkmX8kdspEyoaikx9asrTkwsBzx3KTToS7uP+sApcnbWhWOKgCoPzfprlJerjMp 3Kz5c2q0JV1ka3lByolJGs//cYwh4KwM32i1Ebc5yjlcVskeuKP/dOqbU+NFx0jA a2SWNE7L5YCkJIUOEm327P1muunPc7Q+U/KTaKs0odVIMSg2TO/CW7Y8qaR5LeA8 z8f7AwqUxs87yEgewvRTlSL7YYJ4g== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedufedruddvuddgheduucetufdoteggodetrfdotf 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 A7BBA80060; Fri, 8 Nov 2019 08:17:23 -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 14:17:22 +0100 Message-ID: <1905522.nrmIJexB1b@xps> In-Reply-To: <78a1b1f1-e37b-5f58-10fa-e57efb68b411@solarflare.com> References: <20191025152142.12887-1-pbhagavatula@marvell.com> <1784584.NQqjHnNvIa@xps> <78a1b1f1-e37b-5f58-10fa-e57efb68b411@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 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. > > 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?