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authorMohammed Hawari <mohammed@hawari.fr>2020-09-10 15:10:45 +0200
committerMohammed Hawari <mohammed@hawari.fr>2020-09-10 15:14:30 +0200
commit5d2091da2a96cb1092b0744cdee8bb481788a6dc (patch)
treefc62215b4c8b6a9b4aeada7238edaef0da176025
parent0b31630ce79c4211e00cffd72777413c2408d1fb (diff)
af_xdp: documents incompatibility with 1GB hugepages and high buffers-per-numa.
Type: docs Change-Id: If8602d4b73cc1f04e42d19b8df60a05f67aa90c9 Signed-off-by: Mohammed Hawari <mohammed@hawari.fr>
-rw-r--r--src/plugins/af_xdp/af_xdp_doc.md2
1 files changed, 2 insertions, 0 deletions
diff --git a/src/plugins/af_xdp/af_xdp_doc.md b/src/plugins/af_xdp/af_xdp_doc.md
index 6d2dae55055..40a3596be7c 100644
--- a/src/plugins/af_xdp/af_xdp_doc.md
+++ b/src/plugins/af_xdp/af_xdp_doc.md
@@ -17,6 +17,8 @@ Because of AF_XDP restrictions, the MTU is limited to below PAGE_SIZE
(4096-bytes on most systems) minus 256-bytes, and they are additional
limitations depending upon specific Linux device drivers.
As a rule of thumb, a MTU of 3000-bytes or less should be safe.
+Furthermore, upon UMEM creation, the kernel allocates a physically-contiguous structure, whose size is proportional to the number of 4KB pages contained in the UMEM. That allocation might fail when the number of buffers allocated by VPP is too high. That number can be controlled with the `buffers { buffers-per-numa }` configuration option.
+Finally, note that because of this limitation, this plugin is unlikely to be compatible with the use of 1GB hugepages.
## Requirements
The Linux kernel interface must be up and have enough queues before