From: Yongseok Koh <yskoh@mellanox.com>
To: Olivier Matz <olivier.matz@6wind.com>
Cc: wenzhuo.lu@intel.com, jingjing.wu@intel.com,
adrien.mazarguil@6wind.com, nelio.laranjeiro@6wind.com,
dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v2 1/6] mbuf: add buffer offset field for flexible indirection
Date: Tue, 3 Apr 2018 17:12:06 -0700 [thread overview]
Message-ID: <20180404001205.GB1867@yongseok-MBP.local> (raw)
In-Reply-To: <20180403082615.etnr33cuyey7i3u3@platinum>
On Tue, Apr 03, 2018 at 10:26:15AM +0200, Olivier Matz wrote:
> Hi,
>
> On Mon, Apr 02, 2018 at 11:50:03AM -0700, Yongseok Koh wrote:
> > When attaching a mbuf, indirect mbuf has to point to start of buffer of
> > direct mbuf. By adding buf_off field to rte_mbuf, this becomes more
> > flexible. Indirect mbuf can point to any part of direct mbuf by calling
> > rte_pktmbuf_attach_at().
> >
> > Possible use-cases could be:
> > - If a packet has multiple layers of encapsulation, multiple indirect
> > buffers can reference different layers of the encapsulated packet.
> > - A large direct mbuf can even contain multiple packets in series and
> > each packet can be referenced by multiple mbuf indirections.
> >
> > Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
>
> I think the current API is already able to do what you want.
>
> 1/ Here is a mbuf m with its data
>
> off
> <-->
> len
> +----+ <---------->
> | |
> +-|----v----------------------+
> | | -----------------------|
> m | buf | XXXXXXXXXXX ||
> | -----------------------|
> +-----------------------------+
>
>
> 2/ clone m:
>
> c = rte_pktmbuf_alloc(pool);
> rte_pktmbuf_attach(c, m);
>
> Note that c has its own offset and length fields.
>
>
> off
> <-->
> len
> +----+ <---------->
> | |
> +-|----v----------------------+
> | | -----------------------|
> m | buf | XXXXXXXXXXX ||
> | -----------------------|
> +------^----------------------+
> |
> +----+
> indirect |
> +-|---------------------------+
> | | -----------------------|
> c | buf | ||
> | -----------------------|
> +-----------------------------+
>
> off len
> <--><---------->
>
>
> 3/ remove some data from c without changing m
>
> rte_pktmbuf_adj(c, 10) // at head
> rte_pktmbuf_trim(c, 10) // at tail
>
>
> Please let me know if it fits your needs.
No, it doesn't.
Trimming head and tail with the current APIs removes data and make the space
available. Adjusting packet head means giving more headroom, not shifting the
buffer itself. If m has two indirect mbufs (c1 and c2) and those are pointing to
difference offsets in m,
rte_pktmbuf_adj(c1, 10);
rte_pktmbuf_adj(c2, 20);
then the owner of c2 regard the first (off+20)B as available headroom. If it
wants to attach outer header, it will overwrite the headroom even though the
owner of c1 is still accessing it. Instead, another mbuf (h1) for the outer
header should be linked by h1->next = c2.
If c1 and c2 are attached with shifting buffer address by adjusting buf_off,
which actually shrink the headroom, this case can be properly handled.
And another use-case (this is my actual use-case) is to make a large mbuf have
multiple packets in series. AFAIK, this will also be helpful for some FPGA NICs
because it transfers multiple packets to a single large buffer to reduce PCIe
overhead for small packet traffic like the Multi-Packet Rx of mlx5 does.
Otherwise, packets should be memcpy'd to regular mbufs one by one instead of
indirect referencing.
Does this make sense?
Thanks,
Yongseok
next prev parent reply other threads:[~2018-04-04 0:12 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-10 1:25 [dpdk-dev] [PATCH v1 0/6] net/mlx5: add Multi-Packet Rx support Yongseok Koh
2018-03-10 1:25 ` [dpdk-dev] [PATCH v1 1/6] mbuf: add buffer offset field for flexible indirection Yongseok Koh
2018-03-10 1:25 ` [dpdk-dev] [PATCH v1 2/6] net/mlx5: separate filling Rx flags Yongseok Koh
2018-03-10 1:25 ` [dpdk-dev] [PATCH v1 3/6] net/mlx5: add a function to rdma-core glue Yongseok Koh
2018-03-12 9:13 ` Nélio Laranjeiro
2018-03-10 1:25 ` [dpdk-dev] [PATCH v1 4/6] net/mlx5: add Multi-Packet Rx support Yongseok Koh
2018-03-12 9:20 ` Nélio Laranjeiro
2018-03-10 1:25 ` [dpdk-dev] [PATCH v1 5/6] net/mlx5: release Tx queue resource earlier than Rx Yongseok Koh
2018-03-10 1:25 ` [dpdk-dev] [PATCH v1 6/6] app/testpmd: conserve mbuf indirection flag Yongseok Koh
2018-04-02 18:50 ` [dpdk-dev] [PATCH v2 0/6] net/mlx5: add Multi-Packet Rx support Yongseok Koh
2018-04-02 18:50 ` [dpdk-dev] [PATCH v2 1/6] mbuf: add buffer offset field for flexible indirection Yongseok Koh
2018-04-03 8:26 ` Olivier Matz
2018-04-04 0:12 ` Yongseok Koh [this message]
2018-04-09 16:04 ` Olivier Matz
2018-04-10 1:59 ` Yongseok Koh
2018-04-11 0:25 ` Ananyev, Konstantin
2018-04-11 5:33 ` Yongseok Koh
2018-04-11 11:39 ` Ananyev, Konstantin
2018-04-11 14:02 ` Andrew Rybchenko
2018-04-11 17:18 ` Yongseok Koh
2018-04-11 17:08 ` Yongseok Koh
2018-04-12 16:34 ` Ananyev, Konstantin
2018-04-12 18:58 ` Yongseok Koh
2018-04-02 18:50 ` [dpdk-dev] [PATCH v2 2/6] net/mlx5: separate filling Rx flags Yongseok Koh
2018-04-02 18:50 ` [dpdk-dev] [PATCH v2 3/6] net/mlx5: add a function to rdma-core glue Yongseok Koh
2018-04-02 18:50 ` [dpdk-dev] [PATCH v2 4/6] net/mlx5: add Multi-Packet Rx support Yongseok Koh
2018-04-02 18:50 ` [dpdk-dev] [PATCH v2 5/6] net/mlx5: release Tx queue resource earlier than Rx Yongseok Koh
2018-04-02 18:50 ` [dpdk-dev] [PATCH v2 6/6] app/testpmd: conserve mbuf indirection flag Yongseok Koh
2018-04-19 1:11 ` [dpdk-dev] [PATCH v3 1/2] mbuf: support attaching external buffer to mbuf Yongseok Koh
2018-04-19 1:11 ` [dpdk-dev] [PATCH v3 2/2] app/testpmd: conserve offload flags of mbuf Yongseok Koh
2018-04-23 11:53 ` [dpdk-dev] [PATCH v3 1/2] mbuf: support attaching external buffer to mbuf Ananyev, Konstantin
2018-04-24 2:04 ` Yongseok Koh
2018-04-25 13:16 ` Ananyev, Konstantin
2018-04-25 16:44 ` Yongseok Koh
2018-04-25 18:05 ` Ananyev, Konstantin
2018-04-23 16:18 ` Olivier Matz
2018-04-24 1:29 ` Yongseok Koh
2018-04-24 15:36 ` Olivier Matz
2018-04-24 1:38 ` [dpdk-dev] [PATCH v4 " Yongseok Koh
2018-04-24 1:38 ` [dpdk-dev] [PATCH v4 2/2] app/testpmd: conserve offload flags of mbuf Yongseok Koh
2018-04-24 5:01 ` [dpdk-dev] [PATCH v4 1/2] mbuf: support attaching external buffer to mbuf Stephen Hemminger
2018-04-24 11:47 ` Yongseok Koh
2018-04-24 12:28 ` Andrew Rybchenko
2018-04-24 16:02 ` Olivier Matz
2018-04-24 18:21 ` [dpdk-dev] ***Spam*** " Andrew Rybchenko
2018-04-24 19:15 ` [dpdk-dev] " Olivier Matz
2018-04-24 20:22 ` Thomas Monjalon
2018-04-24 21:53 ` Yongseok Koh
2018-04-24 22:15 ` Thomas Monjalon
2018-04-25 8:21 ` Olivier Matz
2018-04-25 15:06 ` Stephen Hemminger
2018-04-24 23:34 ` Yongseok Koh
2018-04-25 14:45 ` Andrew Rybchenko
2018-04-25 17:40 ` Yongseok Koh
2018-04-25 8:28 ` Olivier Matz
2018-04-25 9:08 ` Yongseok Koh
2018-04-25 9:19 ` Yongseok Koh
2018-04-25 20:00 ` Olivier Matz
2018-04-25 22:54 ` Yongseok Koh
2018-04-24 22:30 ` Yongseok Koh
2018-04-25 2:53 ` [dpdk-dev] [PATCH v5 " Yongseok Koh
2018-04-25 2:53 ` [dpdk-dev] [PATCH v5 2/2] app/testpmd: conserve offload flags of mbuf Yongseok Koh
2018-04-25 13:31 ` [dpdk-dev] [PATCH v5 1/2] mbuf: support attaching external buffer to mbuf Ananyev, Konstantin
2018-04-25 17:06 ` Yongseok Koh
2018-04-25 17:23 ` Ananyev, Konstantin
2018-04-25 18:02 ` Yongseok Koh
2018-04-25 18:22 ` Yongseok Koh
2018-04-25 18:30 ` Yongseok Koh
2018-04-26 1:10 ` [dpdk-dev] [PATCH v6 " Yongseok Koh
2018-04-26 1:10 ` [dpdk-dev] [PATCH v6 2/2] app/testpmd: conserve offload flags of mbuf Yongseok Koh
2018-04-26 11:39 ` [dpdk-dev] [PATCH v6 1/2] mbuf: support attaching external buffer to mbuf Ananyev, Konstantin
2018-04-26 16:05 ` Andrew Rybchenko
2018-04-26 16:10 ` Thomas Monjalon
2018-04-26 19:42 ` Olivier Matz
2018-04-26 19:58 ` Thomas Monjalon
2018-04-26 20:07 ` Olivier Matz
2018-04-26 20:24 ` Thomas Monjalon
2018-04-26 17:18 ` Yongseok Koh
2018-04-26 19:45 ` Olivier Matz
2018-04-27 0:01 ` [dpdk-dev] [PATCH v7 " Yongseok Koh
2018-04-27 0:01 ` [dpdk-dev] [PATCH v7 2/2] app/testpmd: conserve offload flags of mbuf Yongseok Koh
2018-04-27 8:00 ` Andrew Rybchenko
2018-04-27 7:22 ` [dpdk-dev] [PATCH v7 1/2] mbuf: support attaching external buffer to mbuf Andrew Rybchenko
2018-04-27 17:22 ` [dpdk-dev] [PATCH v8 " Yongseok Koh
2018-04-27 17:22 ` [dpdk-dev] [PATCH v8 2/2] app/testpmd: conserve offload flags of mbuf Yongseok Koh
2018-04-27 18:09 ` [dpdk-dev] [PATCH v8 1/2] mbuf: support attaching external buffer to mbuf Thomas Monjalon
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