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From: Thomas Monjalon <thomas.monjalon@6wind.com>
To: Olivier Matz <olivier.matz@6wind.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH RFC 00/11] ixgbe/mbuf: add TSO support
Date: Mon, 19 May 2014 14:47:06 +0200	[thread overview]
Message-ID: <1546716.3aIeLKqHAb@xps13> (raw)
In-Reply-To: <1399647038-15095-1-git-send-email-olivier.matz@6wind.com>

2014-05-09 16:50, Olivier Matz:
> This series add TSO support in ixgbe DPDK driver. As discussed
> previously on the list [1], one problem is that there is not enough room
> in rte_mbuf today to store the required information to implement this
> feature:
>   - a new ol_flag
>   - the MSS
>   - the L4 header len
> 
> A solution would be to increase the size of the mbuf to 2 cache lines
> but it could have a bad impact on performance. This series proposes some
> rework to drastically reduce the size of the rte_mbuf structures before
> implementing the TSO, avoiding to change the mbuf size to 128 bytes.
> 
> After the rework of mbuf structures, the size of rte_mbuf structure is
> reduced by 9 bytes. The implementation of TSO requires to double the
> size of ol_flags (16 to 32 bits) and to double the size of offload
> information in order to add the mss and the l4 header length (32 to 64
> bits). At the end of the whole series, sizeof(rte_mbuf) is still 64
> bytes and 4 bytes are available for future use.
> 
> This rework causes a lot of modifications in the mbuf structure,
> implying some changes in the applications that directly use the mbuf
> structure fields instead of using the API functions (sometimes there is
> no function). That's why this series is a RFC. In my opinion, it's the
> proper moment for this evolution as the 1.7.0 window is open.
> 
> About TSO, the new fields in mbuf try to be generic enough to apply to
> other hardware in the future. To delegate the TCP segmentation to the
> hardware, the user has to:
> 
>   - set the PKT_TX_TCP_SEG flag in mbuf->ol_flags (this flag implies
>     PKT_TX_IP_CKSUM and PKT_TX_TCP_CKSUM)
>   - fill the mbuf->hw_offload information: l2_len, l3_len, l4_len, mss
>   - calculate the pseudo header checksum and set it in the TCP header,
>     as required when doing hardware TCP checksum offload
>   - set the IP checksum to 0

This patchset triggers a lot of interesting discussions about mbuf API, TSO 
and performance impacts.
It seems everybody agree that having TSO support is a nice improvement and 
there are some discussions on how it can be even better.
I feel we need a v2 from Olivier in order to allow us sending improvements 
patches on top of it.

Thanks everyone
-- 
Thomas

      parent reply	other threads:[~2014-05-19 12:47 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-05-09 14:50 Olivier Matz
2014-05-09 14:50 ` [dpdk-dev] [PATCH RFC 01/11] igb/ixgbe: fix IP checksum calculation Olivier Matz
2014-05-15 10:40   ` Ananyev, Konstantin
2014-05-09 14:50 ` [dpdk-dev] [PATCH RFC 02/11] mbuf: rename RTE_MBUF_SCATTER_GATHER into RTE_MBUF_REFCNT Olivier Matz
2014-05-09 14:50 ` [dpdk-dev] [PATCH RFC 03/11] mbuf: remove rte_ctrlmbuf Olivier Matz
2014-05-25 21:39   ` Gilmore, Walter E
2014-05-26 12:23     ` Olivier MATZ
2014-05-26 16:40     ` Dumitrescu, Cristian
2014-05-26 22:43     ` Neil Horman
2014-05-27  0:17   ` Stephen Hemminger
2014-05-28  9:45     ` Ananyev, Konstantin
2014-05-09 14:50 ` [dpdk-dev] [PATCH RFC 04/11] mbuf: remove the rte_pktmbuf structure Olivier Matz
2014-05-09 14:50 ` [dpdk-dev] [PATCH RFC 05/11] mbuf: merge physaddr and buf_len in a bitfield Olivier Matz
2014-05-09 15:39   ` Shaw, Jeffrey B
2014-05-09 16:06     ` Olivier MATZ
2014-05-09 16:11       ` Shaw, Jeffrey B
2014-05-14 14:07         ` Ananyev, Konstantin
2014-05-15  9:53           ` Olivier MATZ
2014-05-19  7:27         ` Olivier MATZ
2014-05-19  8:25           ` Richardson, Bruce
2014-05-19  9:30             ` Olivier MATZ
2014-05-19  9:57               ` Richardson, Bruce
2014-05-09 14:50 ` [dpdk-dev] [PATCH RFC 06/11] mbuf: replace data pointer by an offset Olivier Matz
2014-05-12 14:12   ` Thomas Monjalon
2014-05-12 14:36     ` Venkatesan, Venky
2014-05-12 14:41       ` Neil Horman
2014-05-12 15:07         ` Olivier MATZ
2014-05-12 15:59           ` Stephen Hemminger
2014-05-12 16:13             ` Olivier MATZ
2014-05-12 17:13               ` Stephen Hemminger
2014-05-13 13:29                 ` Olivier MATZ
2014-05-12 16:06           ` Venkatesan, Venky
2014-05-12 18:39             ` Neil Horman
2014-05-13 13:54               ` Venkatesan, Venky
2014-05-13 14:09                 ` Thomas Monjalon
2014-05-09 14:50 ` [dpdk-dev] [PATCH RFC 07/11] mbuf: add functions to get the name of an ol_flag Olivier Matz
2014-05-09 14:50 ` [dpdk-dev] [PATCH RFC 08/11] mbuf: change ol_flags to 32 bits Olivier Matz
2014-05-09 14:50 ` [dpdk-dev] [PATCH RFC 09/11] mbuf: rename vlan_macip_len in hw_offload and increase its size Olivier Matz
2014-05-09 14:50 ` [dpdk-dev] [PATCH RFC 10/11] testpmd: modify source address to validate checksum calculation Olivier Matz
2014-05-09 14:50 ` [dpdk-dev] [PATCH RFC 11/11] ixgbe/mbuf: add TSO support Olivier Matz
2014-05-12 14:30   ` Thomas Monjalon
2014-05-15 15:09   ` Ananyev, Konstantin
2014-05-15 15:39     ` Olivier MATZ
2014-05-15 16:30       ` Ananyev, Konstantin
2014-05-16 12:11         ` Olivier MATZ
2014-05-16 17:01           ` Ananyev, Konstantin
2014-05-19 12:32             ` Thomas Monjalon
2014-05-09 17:04 ` [dpdk-dev] [PATCH RFC 00/11] " Stephen Hemminger
2014-05-09 21:49   ` Olivier MATZ
2014-05-10  0:39     ` Stephen Hemminger
2014-05-19 12:47 ` Thomas Monjalon [this message]

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