feat: flip swap mechanism — MD as primary, RST as override (Phase 1)

This is the first of three phases inverting the per-page swap mechanism
so MD becomes the canonical primary and RST becomes the rare override.

Phase 1 — file renames + conf.py exclude_patterns flip only:
- Rename docs/**/md-<stem>.md to docs/**/<stem>.md (drop md- prefix)
  for all 254 stems previously listed in docs/_swap.txt
- Rename docs/**/<stem>.rst to docs/**/rst-<stem>.rst (add rst- prefix)
  for the same 254 stems
- Repurpose docs/_swap.txt as docs/_rst_overrides.txt; initially empty
  comment-only since no pages need the RST fallback right now
- conf.py exclude_patterns flipped: rst-*.rst is now excluded by default
  instead of md-*.md
- conf.py runtime-artifact references updated to _rst_override_state.json
  and _md_exclude.txt (Phase 2 will rewrite swap_sources.py to produce
  these names; for now no swap script runs because overrides list is empty)

Phase 2 (next commit on this branch) will rewrite scripts/swap_sources.py
with inverted rename direction, delete scripts/import_myst.py + tests, and
update tests/test_swap_sources.py for the new semantics.

Phase 3 will be the cleanup pass and ready-for-review flip.

Generated by robots https://vyos.io

1 files changed, 102 insertions, 0 deletions

diff --git a/docs/vpp/configuration/dataplane/buffers.md b/docs/vpp/configuration/dataplane/buffers.md
new file mode 100644
index 00000000..c9e38a54
--- /dev/null
+++ b/docs/vpp/configuration/dataplane/buffers.md
@@ -0,0 +1,102 @@
+---
+lastproofread: '2026-02-23'
+---
+
+(vpp-config-dataplane-buffers)=
+
+```{include} /_include/need_improvement.txt
+```
+
+
+# VPP Dataplane Buffers Configuration
+
+Buffers are essential for handling network packets efficiently. Proper
+configuration enhances performance and reliability, and is mandatory for
+VPP to work. Buffers temporarily store packets during processing. Therefore,
+their configuration must be in sync with NIC configuration, CPU threads, and
+overall system resources.
+
+:::{important}
+VPP buffers are allocated from the physical memory pool (`physmem`). The
+total amount of memory available for buffer allocation is controlled by the
+`physmem-max-size` setting, while the buffer configuration parameters
+below control how that memory is used for buffer allocation.
+
+See {ref}`VPP Physical Memory Configuration <vpp-config-dataplane-physmem>`
+for details on configuring `physmem`.
+:::
+
+## Buffer Configuration Parameters
+
+The following parameters can be configured for VPP buffers:
+
+### buffers-per-numa
+
+Number of buffers allocated per NUMA node. This setting optimizes
+memory access patterns for multi-CPU systems.
+
+Typically, you need to tune this value if:
+- The system has many interfaces
+- NICs have many queues
+- NICs have large descriptor sizes
+
+Set this value carefully to balance memory usage and performance.
+
+```{cfgcmd} set vpp settings resource-allocation buffers buffers-per-numa \<value\>
+```
+
+The common approach for the calculation is to use the formula:
+
+```none
+buffers-per-numa = (num-rx-queues * num-rx-desc) + (num-tx-queues * num-tx-desc)
+```
+
+Calculate this formula for each NIC and sum the results. Multiply the
+total by 2.5 to get the minimum recommended value for
+`buffers-per-numa`.
+
+Avoid setting this value too low to prevent packet drops.
+
+### data-size
+
+This value sets how much payload data can be stored in a single buffer
+allocated by VPP. Larger values reduce buffer chains for large packets,
+while smaller values conserve memory for environments handling mostly
+small packets.
+
+```{cfgcmd} set vpp settings resource-allocation buffers data-size \<value\>
+```
+
+Optimal size depends on the typical packet size in your network. If
+unsure, use the largest MTU in your network plus overhead (for example,
+128 bytes).
+
+### page-size
+
+A memory pages type used for buffer allocation. Common values are 4K, 2M, or 1G.
+
+Use page sizes configured in your system settings.
+
+```{cfgcmd} set vpp settings resource-allocation buffers page-size \<value\>
+```
+
+
+## Potential Issues and Troubleshooting
+
+Improper buffer configuration can lead to issues such as:
+
+- Increased latency and packet loss
+- Inefficient CPU utilization
+- Interface initialization failures
+
+Indicators of such issues are:
+
+- Errors during interfaces initialization in VPP logs
+- Packet drops observed in VPP statistics
+
+To troubleshoot buffer-related issues, consider the following steps:
+
+- Review VPP logs for errors related to buffer allocation. Look for
+  error `-5` messages.
+- Tune available buffers by adjusting the `buffers-per-numa` and
+  `data-size` parameters.