From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by dpdk.org (Postfix) with ESMTP id 5620A2BA2 for ; Mon, 29 May 2017 14:18:58 +0200 (CEST) Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga104.jf.intel.com with ESMTP; 29 May 2017 05:18:57 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.38,414,1491289200"; d="scan'208";a="1135866681" Received: from bricha3-mobl3.ger.corp.intel.com ([10.237.221.42]) by orsmga001.jf.intel.com with SMTP; 29 May 2017 05:18:54 -0700 Received: by (sSMTP sendmail emulation); Mon, 29 May 2017 13:18:53 +0100 Date: Mon, 29 May 2017 13:18:53 +0100 From: Bruce Richardson To: "Hu, Jiayu" Cc: "Ananyev, Konstantin" , "dev@dpdk.org" , "Wiles, Keith" , "yuanhan.liu@linux.intel.com" Message-ID: <20170529121853.GA34708@bricha3-MOBL3.ger.corp.intel.com> References: <2601191342CEEE43887BDE71AB9772583FAF8C27@IRSMSX109.ger.corp.intel.com> <20170523103154.GA2033@localhost.localdomain> <2601191342CEEE43887BDE71AB9772583FAF9BAE@IRSMSX109.ger.corp.intel.com> <20170526072613.GA85810@localhost.localdomain> <2601191342CEEE43887BDE71AB9772583FAFB22A@IRSMSX109.ger.corp.intel.com> <20170527034137.GA22570@localhost.localdomain> <2601191342CEEE43887BDE71AB9772583FAFE69E@IRSMSX109.ger.corp.intel.com> <20170527140929.GA27976@localhost.localdomain> <2601191342CEEE43887BDE71AB9772583FB02195@IRSMSX109.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Research and =?iso-8859-1?Q?De=ACvel?= =?iso-8859-1?Q?opment?= Ireland Ltd. User-Agent: Mutt/1.8.1 (2017-04-11) Subject: Re: [dpdk-dev] [PATCH v3 1/3] lib: add Generic Receive Offload API framework 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: , X-List-Received-Date: Mon, 29 May 2017 12:19:00 -0000 On Mon, May 29, 2017 at 10:22:57AM +0000, Hu, Jiayu wrote: > Hi Konstantin, > > > -----Original Message----- > > From: Ananyev, Konstantin > > Sent: Sunday, May 28, 2017 12:51 AM > > To: Hu, Jiayu > > Cc: dev@dpdk.org; Wiles, Keith ; > > yuanhan.liu@linux.intel.com > > Subject: RE: [PATCH v3 1/3] lib: add Generic Receive Offload API framework > > > > > > Hi Jiayu, > > > > > > > > Hi Konstantin, > > > > > > On Sat, May 27, 2017 at 07:12:16PM +0800, Ananyev, Konstantin wrote: > > > > > > > > > > > > > -----Original Message----- > > > > > From: Hu, Jiayu > > > > > Sent: Saturday, May 27, 2017 4:42 AM > > > > > To: Ananyev, Konstantin > > > > > Cc: dev@dpdk.org; Wiles, Keith ; > > yuanhan.liu@linux.intel.com > > > > > Subject: Re: [PATCH v3 1/3] lib: add Generic Receive Offload API > > framework > > > > > > > > > > On Sat, May 27, 2017 at 07:10:21AM +0800, Ananyev, Konstantin wrote: > > > > > > Hi Jiayu, > > > > > > > > > > > > > -----Original Message----- > > > > > > > From: Hu, Jiayu > > > > > > > Sent: Friday, May 26, 2017 8:26 AM > > > > > > > To: Ananyev, Konstantin > > > > > > > Cc: dev@dpdk.org; Wiles, Keith ; > > yuanhan.liu@linux.intel.com > > > > > > > Subject: Re: [PATCH v3 1/3] lib: add Generic Receive Offload API > > framework > > > > > > > > > > > > > > Hi Konstantin, > > > > > > > > > > > > > > On Wed, May 24, 2017 at 08:38:25PM +0800, Ananyev, Konstantin > > wrote: > > > > > > > > > > > > > > > > Hi Jiayu, > > > > > > > > > > > > > > > > > > > > > > > > > > Hi Konstantin, > > > > > > > > > > > > > > > > > > Thanks for your comments. My replies/questions are below. > > > > > > > > > > > > > > > > > > BRs, > > > > > > > > > Jiayu > > > > > > > > > > > > > > > > > > On Mon, May 22, 2017 at 05:19:19PM +0800, Ananyev, > > Konstantin wrote: > > > > > > > > > > Hi Jiayu, > > > > > > > > > > My comments/questions below. > > > > > > > > > > Konstantin > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > For applications, DPDK GRO provides three external functions > > to > > > > > > > > > > > enable/disable GRO: > > > > > > > > > > > - rte_gro_init: initialize GRO environment; > > > > > > > > > > > - rte_gro_enable: enable GRO for a given port; > > > > > > > > > > > - rte_gro_disable: disable GRO for a given port. > > > > > > > > > > > Before using GRO, applications should explicitly call > > rte_gro_init to > > > > > > > > > > > initizalize GRO environment. After that, applications can call > > > > > > > > > > > rte_gro_enable to enable GRO and call rte_gro_disable to > > disable GRO for > > > > > > > > > > > specific ports. > > > > > > > > > > > > > > > > > > > > I think this is too restrictive and wouldn't meet various user's > > needs. > > > > > > > > > > User might want to: > > > > > > > > > > - enable/disable GRO for particular RX queue > > > > > > > > > > - or even setup different GRO types for different RX queues, > > > > > > > > > > i.e, - GRO over IPV4/TCP for queue 0, and GRO over > > IPV6/TCP for queue 1, etc. > > > > > > > > > > > > > > > > > > The reason for enabling/disabling GRO per-port instead of per- > > queue is that LINUX > > > > > > > > > controls GRO per-port. To control GRO per-queue indeed can > > provide more flexibility > > > > > > > > > to applications. But are there any scenarios that different > > queues of a port may > > > > > > > > > require different GRO control (i.e. GRO types and enable/disable > > GRO)? > > > > > > > > > > > > > > > > I think yes. > > > > > > > > > > > > > > > > > > > > > > > > > > > - For various reasons, user might prefer not to use RX callbacks > > for various reasons, > > > > > > > > > > But invoke gro() manually at somepoint in his code. > > > > > > > > > > > > > > > > > > An application-used GRO library can enable more flexibility to > > applications. Besides, > > > > > > > > > when perform GRO in ethdev layer or inside PMD drivers, it is an > > issue that > > > > > > > > > rte_eth_rx_burst returns actually received packet number or > > GROed packet number. And > > > > > > > > > the same issue happens in GSO, and even more seriously. This is > > because applications > > > > > > > > > , like VPP, always rely on the return value of rte_eth_tx_burst to > > decide further > > > > > > > > > operations. If applications can direcly call GRO/GSO libraries, > > this issue won't exist. > > > > > > > > > And DPDK is a library, which is not a holistic system like LINUX. > > We don't need to do > > > > > > > > > the same as LINUX. Therefore, maybe it's a better idea to > > directly provide SW > > > > > > > > > segmentation/reassembling libraries to applications. > > > > > > > > > > > > > > > > > > > - Many users would like to control size (number of flows/items > > per flow), > > > > > > > > > > max allowed packet size, max timeout, etc., for different GRO > > tables. > > > > > > > > > > - User would need a way to flush all or only timeout packets > > from particular GRO tables. > > > > > > > > > > > > > > > > > > > > So I think that API needs to extended to become be much more > > fine-grained. > > > > > > > > > > Something like that: > > > > > > > > > > > > > > > > > > > > struct rte_gro_tbl_param { > > > > > > > > > > int32_t socket_id; > > > > > > > > > > size_t max_flows; > > > > > > > > > > size_t max_items_per_flow; > > > > > > > > > > size_t max_pkt_size; > > > > > > > > > > uint64_t packet_timeout_cycles; > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ... > > > > > > > > > > }; > > > > > > > > > > > > > > > > > > > > struct rte_gro_tbl; > > > > > > > > > > strct rte_gro_tbl *rte_gro_tbl_create(const struct > > rte_gro_tbl_param *param); > > > > > > > > > > > > > > > > > > > > void rte_gro_tbl_destroy(struct rte_gro_tbl *tbl); > > > > > > > > > > > > > > > > > > Yes, I agree with you. It's necessary to provide more fine- > > grained control APIs to > > > > > > > > > applications. But what's 'packet_timeout_cycles' used for? Is it > > for TCP packets? > > > > > > > > > > > > > > > > For any packets that sits in the gro_table for too long. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > /* > > > > > > > > > > * process packets, might store some packets inside the GRO > > table, > > > > > > > > > > * returns number of filled entries in pkt[] > > > > > > > > > > */ > > > > > > > > > > uint32_t rte_gro_tbl_process(struct rte_gro_tbl *tbl, struct > > rte_mbuf *pkt[], uint32_t num); > > > > > > > > > > > > > > > > > > > > /* > > > > > > > > > > * retirieves up to num timeouted packets from the table. > > > > > > > > > > */ > > > > > > > > > > uint32_t rtre_gro_tbl_timeout(struct rte_gro_tbl *tbl, uint64_t > > tmt, struct rte_mbuf *pkt[], uint32_t num); > > > > > > > > > > > > > > > > > > Currently, we implement GRO as RX callback, whose processing > > logic is simple: > > > > > > > > > receive burst packets -> perform GRO -> return to application. > > GRO stops after > > > > > > > > > finishing processing received packets. If we provide > > rte_gro_tbl_timeout, when > > > > > > > > > and who will call it? > > > > > > > > > > > > > > > > I mean the following scenario: > > > > > > > > We receive a packet, find it is eligible for GRO and put it into > > gro_table > > > > > > > > in expectation - there would be more packets for the same flow. > > > > > > > > But it could happen that we would never (or for some long time) > > receive > > > > > > > > any new packets for that flow. > > > > > > > > So the first packet would never be delivered to the upper layer, > > > > > > > > or delivered too late. > > > > > > > > So we need a mechanism to extract such not merged packets > > > > > > > > and push them to the upper layer. > > > > > > > > My thought it would be application responsibility to call it from > > time to time. > > > > > > > > That's actually another reason why I think we shouldn't use > > application > > > > > > > > to always use RX callbacks for GRO. > > > > > > > > > > > > > > Currently, we only provide one reassembly function, > > rte_gro_reassemble_burst, > > > > > > > which merges N inputted packets at a time. After finishing > > processing these > > > > > > > packets, it returns all of them and reset hashing tables. Therefore, > > there > > > > > > > are no packets in hashing tables after rte_gro_reassemble_burst > > returns. > > > > > > > > > > > > Ok, sorry I missed that part with rte_hash_reset(). > > > > > > So gro_ressemble_burst() performs only inline processing on current > > input packets > > > > > > and doesn't try to save packets for future merging, correct? > > > > > > > > > > Yes. > > > > > > > > > > > Such approach indeed is much lightweight and doesn't require any > > extra timeouts and flush(). > > > > > > So my opinion let's keep it like that - nice and simple. > > > > > > BTW, I think in that case we don't need any hashtables (or any other > > persistent strucures)at all. > > > > > > What we need is just a set of GROs (tcp4, tpc6, etc.) we want to > > perform on given array of packets. > > > > > > > > > > Beside GRO types that are desired to perform, maybe it also needs > > max_pkt_size and > > > > > some GRO type specific information? > > > > > > > > Yes, but we don't need the actual hash-tables, etc. inside. > > > > Passing something like struct gro_param seems enough. > > > > > > Yes, we can just pass gro_param and allocate hashing tables > > > inside rte_gro_reassemble_burst. If so, hashing tables of > > > desired GRO types are created and freed in each invocation > > > of rte_gro_reassemble_burst. In GRO library, hashing tables > > > are created by GRO type specific gro_tbl_create_fn. These > > > gro_tbl_create_fn may allocate hashing table space via malloc > > > (or rte_malloc). Therefore, we may frequently call malloc/free > > > when using rte_gro_reassemble_burst. In my opinion, it will > > > degrade GRO performance greatly. > > > > I don't' understand why do we need to put/extract each packet into/from > > hash table at all. > > We have N input packets that need to be grouped/sorted by some criteria. > > Surely that can be done without any hash-table involved. > > What is the need for hash table and all the overhead it brings here? > > In current design, I assume all GRO types use hash tables to merge > packets. The key of the hash table is the criteria to merge packets. > So the main difference for different GRO types' hash tables is the > key definition. > > And the reason for using hash tables is to speed up reassembly. Given > There are N TCP packets inputted, the simplest way to process packets[i] > Is to traverse processed packets[0]~packets[i-1] and try to find a one > to merge. In the worst case, we need to check all of packets[0~i-1]. > In this case, the time complexity of processing N packets is O(N^2). > If we use a hash table, whose key is the criteria to merge two packets, > the time to find a packet that may be merged with packets[i] is O(1). > > Do you think it's too complicated? > > Jiayu > How big is your expected burst size? If you are expecting 32 or 64 packets per call, then N is small and the overhead of the hash table seems a bit much. Perhaps you need different code paths for bigger and smaller bursts? /Bruce