On 2/7/2022 7:49 AM, Loftus, Ciara wrote:
On 2/4/2022 12:54 PM, Ciara Loftus wrote:
Secondary process support had been disabled for the AF_XDP PMD
because there was no logic in place to share the AF_XDP socket
file descriptors between the processes. This commit introduces
this logic using the IPC APIs.
Since AF_XDP rings are single-producer single-consumer, rx/tx
in the secondary process is disabled. However other operations
including retrieval of stats are permitted.
Signed-off-by: Ciara Loftus <ciara.lof...@intel.com>
---
v1 -> v2:
* Rebase to next-net
RFC -> v1:
* Added newline to af_xdp.rst
* Fixed spelling errors
* Fixed potential NULL dereference in init_internals
* Fixed potential free of address-of expression in afxdp_mp_request_fds
---
doc/guides/nics/af_xdp.rst | 9 ++
doc/guides/nics/features/af_xdp.ini | 1 +
doc/guides/rel_notes/release_22_03.rst | 1 +
drivers/net/af_xdp/rte_eth_af_xdp.c | 210
+++++++++++++++++++++++--
4 files changed, 207 insertions(+), 14 deletions(-)
diff --git a/doc/guides/nics/af_xdp.rst b/doc/guides/nics/af_xdp.rst
index db02ea1984..eb4eab28a8 100644
--- a/doc/guides/nics/af_xdp.rst
+++ b/doc/guides/nics/af_xdp.rst
@@ -141,4 +141,13 @@ Limitations
NAPI context from a watchdog timer instead of from softirqs. More
information
on this feature can be found at [1].
+- **Secondary Processes**
+
+ Rx and Tx are not supported for secondary processes due to the single-
producer
+ single-consumer nature of the AF_XDP rings. However other operations
including
+ statistics retrieval are permitted.
Hi Ciara,
Isn't this limitation same for all PMDs, like not both primary & secondary can
Rx/Tx
from same queue at the same time.
But primary can initiallize the PMD and secondary can do the datapath,
or isn't af_xdp supports multiple queue, if so some queues can be used by
primary and some by secondary for datapath.
Is there anyhing special for af_xdp that prevents it?
Hi Ferruh,
Thanks for the review.
Each queue of the PMD corresponds to a new AF_XDP socket.
Each socket has an RX and TX ring that is mmapped from the kernel to userspace
and this mapping is only valid for the primary process.
I did not figure out a way to share that mapping with the secondary process
successfully. Can you think of anything that might work?
Does the application knows the buffer address for the Rx/Tx, or is
abstracted to the 'fd'?
If only 'fd' is used, this patch already converts 'fd' between
processes.
cc'ed Anatoly, but what I understand is after MP fd conversion:
Primary process: FD=x
Secondary process: FD=y
And both x & y points to exact same socket in the kernel side.
At least this is how it works for the 'tap' interface, and that is
why 'fs' are in the process_private area and converted between primary
and secondary, I thought it will be same for the xdp socket.
Did you test the secondary Rx/Tx in the secondary after this patch?
