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From: Olivier Matz <olivier.matz@6wind.com>
To: Nithin Dabilpuram <ndabilpuram@marvell.com>
Cc: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
	Jerin Jacob <jerinjacobk@gmail.com>,
	"Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>,
	Nithin Dabilpuram <nithind1988@gmail.com>,
	Thomas Monjalon <thomas@monjalon.net>,
	"Yigit, Ferruh" <ferruh.yigit@intel.com>,
	Andrew Rybchenko <arybchenko@solarflare.com>,
	Ori Kam <orika@mellanox.com>,
	"Burakov, Anatoly" <anatoly.burakov@intel.com>,
	"Mcnamara, John" <john.mcnamara@intel.com>,
	"Kovacevic, Marko" <marko.kovacevic@intel.com>,
	dpdk-dev <dev@dpdk.org>, Jerin Jacob <jerinj@marvell.com>,
	Krzysztof Kanas <kkanas@marvell.com>,
	"techboard@dpdk.org" <techboard@dpdk.org>
Subject: Re: [dpdk-dev] [EXT] Re: [PATCH 1/3] mbuf: add Tx offloads for packet marking
Date: Wed, 3 Jun 2020 10:28:44 +0200	[thread overview]
Message-ID: <20200603082844.GG12564@platinum> (raw)
In-Reply-To: <20200602142537.GA6274@outlook.office365.com>

Hi,

On Tue, Jun 02, 2020 at 07:55:37PM +0530, Nithin Dabilpuram wrote:
> On Tue, Jun 02, 2020 at 10:53:08AM +0000, Ananyev, Konstantin wrote:
> > Hi Jerin,
> > 
> > > > > > I also share Olivier's concern about consuming 3 bits in ol_flags for that feature.
> > > > > > Can it probably be squeezed somehow?
> > > > > > Let say we reserve one flag that this information is present or not, and
> > > > > > re-use one of rx-only fields for store additional information (packet_type, or so).
> > > > > > Or might be some other approach.
> > > > >
> > > > > We are fine with this approach where we define one bit in Tx offloads for pkt
> > > > > marking and and 3 bits reused from Rx offload flags area.
> > > > >
> > > > > For example:
> > > > >
> > > > > @@ -186,10 +186,16 @@ extern "C" {
> > > > >
> > > > >  /* add new RX flags here, don't forget to update PKT_FIRST_FREE */
> > > > >
> > > > > +/* Reused Rx offload bits for Tx offloads */
> > > > > +#define PKT_X_TX_MARK_VLAN_DEI         (1ULL << 0)
> > > > > +#define PKT_X_TX_MARK_IP_DSCP          (1ULL << 1)
> > > > > +#define PKT_X_TX_MARK_IP_ECN           (1ULL << 2)
> > > > > +
> > > > >  #define PKT_FIRST_FREE (1ULL << 23)
> > > > > -#define PKT_LAST_FREE (1ULL << 40)
> > > > > +#define PKT_LAST_FREE (1ULL << 39)
> > > > >
> > > > >  /* add new TX flags here, don't forget to update PKT_LAST_FREE  */
> > > > > +#define PKT_TX_MARK_EN         (1ULL << 40)
> > > > >
> > > > > Is this fine ?
> > > >
> > > > Any thoughts on this approach which uses only 1 bit in Tx flags out of 18
> > > > and reuse unused Rx flag bits ?
> > 
> > My thought was not about re-defining the flags (I think it is better to keep them intact),
> > but adding a union for one of rx-only fields (packet_type/rss/timestamp).
> 
> Ok. Adding a union field at packet_type field is also fine like below. 
> 
> @@ -187,9 +187,10 @@ extern "C" {
>  /* add new RX flags here, don't forget to update PKT_FIRST_FREE */
>  
>  #define PKT_FIRST_FREE (1ULL << 23)
> -#define PKT_LAST_FREE (1ULL << 40)
> +#define PKT_LAST_FREE (1ULL << 39)
>  
>  /* add new TX flags here, don't forget to update PKT_LAST_FREE  */
> +#define PKT_TX_MARK_EN		(1ULL << 40)
>  
>  /**
>   * Outer UDP checksum offload flag. This flag is used for enabling
> @@ -461,6 +462,14 @@ enum {
>  #endif
>  };
>  
> +/* Tx packet marking flags in rte_mbuf::tx_mark.
> + * Valid only when PKT_TX_MARK_EN is set in
> + * rte_mbuf::ol_flags.
> + */
> +#define TX_MARK_VLAN_DEI	(1ULL << 0)
> +#define TX_MARK_IP_DSCP	(1ULL << 1)
> +#define TX_MARK_IP_ECN		(1ULL << 2)
> +
>  /**
>   * The generic rte_mbuf, containing a packet mbuf.
>   */
> @@ -543,6 +552,10 @@ struct rte_mbuf {
>  			};
>  			uint32_t inner_l4_type:4; /**< Inner L4 type. */
>  		};
> +		struct {
> +			uint32_t reserved:29;
> +			uint32_t tx_mark:3;
> +		};
>  	};
> 
> 
> 
> Please correct me if this is not what you mean.

I'm not a big fan of reusing Rx fields or flags for Tx.
It's not obvious for an application than adding a tx_mark will overwrite
the packet_type. I understand that the risk is limited because packet_type
is Rx and the marks are Tx, but there is still one.

To summarize the different proposed approaches (please correct me if I'm wrong):

a- add 3 Tx mbuf flags
   (-) consumes limited resource

b- add 3 dynamic flags
   (-) slower

c- add 1 Tx flag and union with Rx field
   (-) exclusive with Rx field
   (-) still consumes one flag

My preference is still b-, for these reasons:

- There are many different DPDK use cases, and resources in mbuf is tight.
  Recent contributions (rte_flow and ice driver) already made use of dynamic
  fields/flags.

- When I implemented the dynamic fields/flags feature, I did a test which
  showed that the cost of having a dynamic offset was few cycles (on my test
  platform, it was~3 cycles for reading a field and ~2 cycles for writing a
  field).

Regards,
Olivier

> 
> > 
> > > 
> > > + Techboard
> > > 
> > > There is a related thread going on
> > > https://urldefense.proofpoint.com/v2/url?u=http-3A__mails.dpdk.org_archives_dev_2020-2DMay_168810.html&d=DwIGaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r=FZ_tPCbgFOh18zwRPO9H0yDx8VW38vuapifdDfc8SFQ&m=nyV4Rud03HW6DbWMpyvOCulQNkagmfo0wKtrwQ7zmmg&s=VuktoUb_xoLsHKdB9mV87x67cP9tXk3DqVXptt9nF_s&e= 
> > > 
> > > If there is no consensus on email, then I would like to add this item
> > > to the next TB meeting.
> > 
> > Ok, I'll add that to tomorrow meeting agenda.
> > Konstantin
> > 



  reply	other threads:[~2020-06-03  8:28 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-17  7:22 [dpdk-dev] " Nithin Dabilpuram
2020-04-17  7:22 ` [dpdk-dev] [PATCH 2/3] net/octeontx2: add tm packet marking cb Nithin Dabilpuram
2020-04-17  7:22 ` [dpdk-dev] [PATCH 3/3] net/octeontx2: add Tx packet marking offload support Nithin Dabilpuram
2020-05-01 11:18 ` [dpdk-dev] [PATCH 1/3] mbuf: add Tx offloads for packet marking Jerin Jacob
2020-05-04  8:06   ` Olivier Matz
2020-05-04  8:27     ` [dpdk-dev] [EXT] " Nithin Dabilpuram
2020-05-04  9:16       ` Olivier Matz
2020-05-04 10:04         ` Nithin Dabilpuram
2020-05-04 12:27           ` Olivier Matz
2020-05-05  6:19             ` Nithin Dabilpuram
2020-05-13 12:28               ` Nithin Dabilpuram
2020-05-14 20:29               ` Olivier Matz
2020-05-15 10:08                 ` Nithin Dabilpuram
2020-05-15 10:30                   ` Ananyev, Konstantin
2020-05-15 13:57                     ` Nithin Dabilpuram
2020-05-28 15:43                       ` Nithin Dabilpuram
2020-05-30 15:12                         ` Jerin Jacob
2020-06-02 10:53                           ` Ananyev, Konstantin
2020-06-02 14:25                             ` Nithin Dabilpuram
2020-06-03  8:28                               ` Olivier Matz [this message]
2020-06-03 10:44                                 ` Nithin Dabilpuram
2020-06-03 11:38                                   ` Olivier Matz
2020-06-03 12:52                                     ` Nithin Dabilpuram
2020-06-03 16:14                                       ` Slava Ovsiienko
2020-06-08  9:39                                         ` Nithin Dabilpuram
2020-06-03 14:56                                     ` Thomas Monjalon
2020-06-03 10:31                               ` Ananyev, Konstantin
2020-05-15 13:12                   ` Thomas Monjalon
2020-05-15 13:44                     ` Nithin Dabilpuram
2020-05-15 15:10                       ` Thomas Monjalon
2020-05-15 16:26                         ` Jerin Jacob
2020-05-15 16:52                           ` Thomas Monjalon
2020-05-15 17:00                             ` Jerin Jacob
2020-05-15 18:07                             ` Nithin Dabilpuram
2023-07-31 12:54 ` [dpdk-dev] " Thomas Monjalon
2023-08-14  8:11   ` Nithin Dabilpuram

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