On 6/7/22 13:13, Ding, Xuan wrote:
Hi Andrew,
-----Original Message-----
From: Andrew Rybchenko <andrew.rybche...@oktetlabs.ru>
Sent: Saturday, June 4, 2022 10:26 PM
To: Ding, Xuan <xuan.d...@intel.com>; Wu, WenxuanX
<wenxuanx...@intel.com>; tho...@monjalon.net; Li, Xiaoyun
<xiaoyun...@intel.com>; ferruh.yi...@xilinx.com; Singh, Aman Deep
<aman.deep.si...@intel.com>; dev@dpdk.org; Zhang, Yuying
<yuying.zh...@intel.com>; Zhang, Qi Z <qi.z.zh...@intel.com>;
jerinjac...@gmail.com
Cc: step...@networkplumber.org; Wang, YuanX <yuanx.w...@intel.com>;
Ray Kinsella <m...@ashroe.eu>
Subject: Re: [PATCH v8 1/3] ethdev: introduce protocol hdr based buffer split
On 6/3/22 19:30, Ding, Xuan wrote:
Hi Andrew,
-----Original Message-----
From: Andrew Rybchenko <andrew.rybche...@oktetlabs.ru>
Sent: Thursday, June 2, 2022 9:21 PM
To: Wu, WenxuanX <wenxuanx...@intel.com>; tho...@monjalon.net;
Li,
Xiaoyun <xiaoyun...@intel.com>; ferruh.yi...@xilinx.com; Singh, Aman
Deep <aman.deep.si...@intel.com>; dev@dpdk.org; Zhang, Yuying
<yuying.zh...@intel.com>; Zhang, Qi Z <qi.z.zh...@intel.com>;
jerinjac...@gmail.com
Cc: step...@networkplumber.org; Ding, Xuan <xuan.d...@intel.com>;
Wang, YuanX <yuanx.w...@intel.com>; Ray Kinsella <m...@ashroe.eu>
Subject: Re: [PATCH v8 1/3] ethdev: introduce protocol hdr based
buffer split
Is it the right one since it is listed in patchwork?
Yes, it is.
On 6/1/22 16:50, wenxuanx...@intel.com wrote:
From: Wenxuan Wu <wenxuanx...@intel.com>
Currently, Rx buffer split supports length based split. With Rx
queue offload RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT enabled and Rx
packet
segment
configured, PMD will be able to split the received packets into
multiple segments.
However, length based buffer split is not suitable for NICs that do
split based on protocol headers. Given a arbitrarily variable length
in Rx packet
a -> an
Thanks for your catch, will fix it in next version.
segment, it is almost impossible to pass a fixed protocol header to PMD.
Besides, the existence of tunneling results in the composition of a
packet is various, which makes the situation even worse.
This patch extends current buffer split to support protocol header
based buffer split. A new proto_hdr field is introduced in the
reserved field of rte_eth_rxseg_split structure to specify protocol
header. The proto_hdr field defines the split position of packet,
splitting will always happens after the protocol header defined in
the Rx packet segment. When Rx queue offload
RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT is enabled and corresponding
protocol
header is configured, PMD will split the ingress packets into
multiple
segments.
struct rte_eth_rxseg_split {
struct rte_mempool *mp; /* memory pools to allocate
segment from
*/
uint16_t length; /* segment maximal data length,
configures "split point" */
uint16_t offset; /* data offset from beginning
of mbuf data buffer */
uint32_t proto_hdr; /* inner/outer L2/L3/L4 protocol header,
configures "split point" */
};
Both inner and outer L2/L3/L4 level protocol header split can be
supported.
Corresponding protocol header capability is RTE_PTYPE_L2_ETHER,
RTE_PTYPE_L3_IPV4, RTE_PTYPE_L3_IPV6, RTE_PTYPE_L4_TCP,
RTE_PTYPE_L4_UDP, RTE_PTYPE_L4_SCTP, RTE_PTYPE_INNER_L2_ETHER,
RTE_PTYPE_INNER_L3_IPV4, RTE_PTYPE_INNER_L3_IPV6,
RTE_PTYPE_INNER_L4_TCP, RTE_PTYPE_INNER_L4_UDP,
RTE_PTYPE_INNER_L4_SCTP.
For example, let's suppose we configured the Rx queue with the
following segments:
seg0 - pool0, proto_hdr0=RTE_PTYPE_L3_IPV4, off0=2B
seg1 - pool1, proto_hdr1=RTE_PTYPE_L4_UDP, off1=128B
seg2 - pool2, off1=0B
The packet consists of MAC_IPV4_UDP_PAYLOAD will be split like
following:
seg0 - ipv4 header @ RTE_PKTMBUF_HEADROOM + 2 in mbuf from
pool0
seg1 - udp header @ 128 in mbuf from pool1
seg2 - payload @ 0 in mbuf from pool2
It must be defined how ICMPv4 packets will be split in such case.
And how UDP over IPv6 will be split.
The ICMP header type is missed, I will define the expected split
behavior and add it in next version, thanks for your catch.
I have a question here. Since ICMP packets are mainly used to check the
connectivity of network, is it necessary for us to split ICMP packets?
And I found there is no RTE_PTYPE for ICMP.
I'm not saying that we should split on ICMP. I'm just saying that we
must define the behaviour when happens for packets which do not match
split specification. Does it split on longest match and everything else
is put in (which?) last buffer? E.g. we configure split on ETH-IPv4-TCP.
What does happen with ETH-IPv4-UDP? ETH-IPv6?
In fact, the buffer split based on protocol header depends on the driver
parsing result.
As long as driver can recognize this packet type, I think there is no
difference between UDP over IPV4 and UDP over IPV6?
We can bind it to ptypes recognized by the HW+driver, but I can easily
imagine the case when HW has no means to report recognized packet type
(i.e. ptype get returns empty list), but still could split on it.
Get your point. But if one ptype cannot be recognized by HW+driver, is it still
necessary for
us to do the split? The main purpose of buffer split is to split header and
payload. Although we
add split for various protocol headers now, we should focus the ptype can be
recognized.
Recognition and reporting is a separate things. It could be recognized,
but it can have no means to report it to the driver. ptype_get is about
reporting.
Also, nobody guarantees that there is no different in UDP over IPv4 vs
IPv6 recognition and split. IPv6 could have a number of extension headers
which could be not that trivial to hop in HW. So, HW could recognize IPv6,
but not protocols after it.
Also it is very interesting question how to define protocol split for IPv6 plus
extension headers. Where to stop?
The extension header you mentioned is indeed an interesting question.
On our device, the stop would be the end of extension header. The same as
above, the main purpose of buffers split is for header and payload.
Even rte_flow, we don't list all of the extension headers. So we can't cope with
all the IPV6 extension headers.
Again, we must define the behaviour. Application needs to know what to
expect.
For IPV6 extension headers, what if we treat the IPV6 header and extension
header as one layer? Because 99% of cases will not require a separate extension
header.
I'd like to highlight that it is not "an extension header". It is
'extension headers' (plural). I'm not sure that we can say that
in order to split on IPv6 HW must support *all* (even future)
extension headers.
Hope to get your insights.
Unfortunately I have no solutions. Just questions to be answered...
Now buffet split can be configured in two modes. For length based
buffer split, the mp, length, offset field in Rx packet segment
should be configured, while the proto_hdr field should not be configured.
For protocol header based buffer split, the mp, offset, proto_hdr
field in Rx packet segment should be configured, while the length
field should not be configured.
The split limitations imposed by underlying PMD is reported in the
rte_eth_dev_info->rx_seg_capa field. The memory attributes for the
split parts may differ either, dpdk memory and external memory,
respectively.
Signed-off-by: Xuan Ding <xuan.d...@intel.com>
Signed-off-by: Yuan Wang <yuanx.w...@intel.com>
Signed-off-by: Wenxuan Wu <wenxuanx...@intel.com>
Reviewed-by: Qi Zhang <qi.z.zh...@intel.com>
Acked-by: Ray Kinsella <m...@ashroe.eu>
---
lib/ethdev/rte_ethdev.c | 40 +++++++++++++++++++++++++++++++++---
----
lib/ethdev/rte_ethdev.h | 28 +++++++++++++++++++++++++++-
2 files changed, 60 insertions(+), 8 deletions(-)
diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c index
29a3d80466..fbd55cdd9d 100644
--- a/lib/ethdev/rte_ethdev.c
+++ b/lib/ethdev/rte_ethdev.c
@@ -1661,6 +1661,7 @@ rte_eth_rx_queue_check_split(const struct
rte_eth_rxseg_split *rx_seg,
struct rte_mempool *mpl = rx_seg[seg_idx].mp;
uint32_t length = rx_seg[seg_idx].length;
uint32_t offset = rx_seg[seg_idx].offset;
+ uint32_t proto_hdr = rx_seg[seg_idx].proto_hdr;
if (mpl == NULL) {
RTE_ETHDEV_LOG(ERR, "null mempool pointer\n");
@@ -1694,13
+1695,38 @@ rte_eth_rx_queue_check_split(const struct
rte_eth_rxseg_split *rx_seg,
}
offset += seg_idx != 0 ? 0 : RTE_PKTMBUF_HEADROOM;
*mbp_buf_size = rte_pktmbuf_data_room_size(mpl);
- length = length != 0 ? length : *mbp_buf_size;
- if (*mbp_buf_size < length + offset) {
- RTE_ETHDEV_LOG(ERR,
- "%s mbuf_data_room_size %u < %u
(segment length=%u + segment offset=%u)\n",
- mpl->name, *mbp_buf_size,
- length + offset, length, offset);
- return -EINVAL;
+ if (proto_hdr == RTE_PTYPE_UNKNOWN) {
+ /* Split at fixed length. */
+ length = length != 0 ? length : *mbp_buf_size;
+ if (*mbp_buf_size < length + offset) {
+ RTE_ETHDEV_LOG(ERR,
+ "%s mbuf_data_room_size %u < %u
(segment length=%u + segment offset=%u)\n",
+ mpl->name, *mbp_buf_size,
+ length + offset, length, offset);
+ return -EINVAL;
+ }
+ } else {
+ /* Split after specified protocol header. */
+ if (!(proto_hdr &
RTE_BUFFER_SPLIT_PROTO_HDR_MASK)) {
The condition looks suspicious. It will be true if proto_hdr has no
single bit from the mask. I guess it is not the intent.
Actually it is the intent... Here the mask is used to check if
proto_hdr belongs to the inner/outer L2/L3/L4 capability we defined.
And which proto_hdr is supported by the NIC will be checked in the PMD
later.
Need to correct here. You are right, I made a bug in previous implementation.
Frankly speaking I see no value in such incomplete check if we still rely on
driver. I simply see no reason to oblige the driver to support one of these
protocols.
With API, we can get the driver's capabilities first, and do the check in
ethdev later.
In this way, we can finish the checks in once. Please see v9.
I guess the condition should be
proto_hdr & ~RTE_BUFFER_SPLIT_PROTO_HDR_MASK i.e. there is
unsupported bits in proto_hdr
IMHO we need extra field in dev_info to report supported protocols to
split on. Or a new API to get an array similar to ptype get.
May be a new API is a better choice to not overload dev_info and to
be more flexible in reporting.
Thanks for your suggestion.
Here I hope to confirm the intent of dev_info or API to expose the
supported proto_hdr of driver.
Is it for the pro_hdr check in the rte_eth_rx_queue_check_split()?
If so, could we just check whether pro_hdrs configured belongs to
L2/L3/L4 in lib, and check the capability in PMD? This is what the current
design does.
Look. Application needs to know what to expect from eth device.
It should know which protocols it can split on. Of course we can enforce
application to use try-fail approach which would make sense if we have
dedicated API to request Rx buffer split, but since it is done via Rx queue
configuration, it could be tricky for application to realize which part of the
configuration is wrong. It could simply result in a too many retries with
different configuration.
Agree. To avoid the unnecessary try-fails, I will add a new API in dev_ops,
please see v9.
I.e. the information should be used by ethdev to validate request and the
information should be ued by the application to understand what is
supported.
Actually I have another question, do we need a API or dev_info to expose
which buffer split the driver supports.
i.e. length based or proto_hdr based. Because it requires different
fields to be configured in RX packet segment.
See above. If dedicated API return -ENOTSUP or empty set of supported
protocols to split on, the answer is clear.
Get your point. I totally agree with your idea of a new API.
Through the API, the logic will look like:
ret = rte_get_supported_buffer_split_proto();
if (ret == -ENOTSUP)
Check length based buffer split
else
Checked proto based buffer split
We don't need to care about the irrelevant fields in respective
buffer split anymore.
BTW, could you help to review the deprecation notice for header split?
If it gets acked, I will start the deprecation in 22.11.
Since the feature is definitely dead. I'd use faster track.
Deprecate in 22.07 and remove in 22.11.
Thanks,
Xuan
Hope to get your insights. :)
+ RTE_ETHDEV_LOG(ERR,
+ "Protocol header %u not
supported)\n",
+ proto_hdr);
I think it would be useful to log unsupported bits only, if we say so.
The same as above.
Thanks again for your time.
Regards,
Xuan
