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, 142 insertions, 0 deletions

diff --git a/docs/vpp/configuration/dataplane/memory.md b/docs/vpp/configuration/dataplane/memory.md
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+---
+lastproofread: '2026-02-27'
+---
+
+(vpp_config_dataplane_memory)=
+
+```{include} /_include/need_improvement.txt
+```
+
+# VPP Memory Configuration
+
+VPP heavily relies on hugepages for its memory management. Hugepages
+are larger memory pages that reduce the overhead of page management and
+improve performance for applications that require large amounts of
+memory, such as VPP.
+
+VPP supports both 2MB and 1GB hugepages, but the default and most
+commonly used size is 2MB. The choice of hugepage size can impact
+performance, with larger pages generally providing better performance
+for memory-intensive applications.
+
+Before configuring memory in VPP dataplane settings, you need to
+ensure that hugepages are enabled and properly configured on your
+system.
+
+:::{seealso}
+{ref}`Hugepages in VyOS Configuration for VPP <vpp-config-hugepages>`
+:::
+
+To configure memory settings for VPP, you can use the following
+commands in the VPP CLI:
+
+VPP uses a main heap as a central memory pool for FIB data structures
+entry allocations.
+
+Efficient memory management is crucial for VPP's performance, and the
+main heap plays a significant role in this.
+
+It can be configured using the following command:
+
+```{cfgcmd} set vpp settings resource-allocation memory main-heap-page-size \<size\>
+```
+
+Sets the main heap page size for VPP.
+
+```{cfgcmd} set vpp settings resource-allocation memory main-heap-size \<size\>
+```
+
+Sets the main heap size for VPP.
+(vpp-config-dataplane-physmem)=
+
+## Physical Memory Configuration
+
+VPP uses physical memory for packet buffers and interface operations.
+The `physmem` setting controls how much memory VPP can allocate for
+these operations.
+
+```{cfgcmd} set vpp settings resource-allocation memory physmem-max-size \<size\>
+```
+
+Sets the maximum amount of physical memory VPP can use for packet
+processing and interface buffers.
+
+**Default**: 16GB (usually sufficient for most deployments)
+
+You may need to modify the value for high-throughput environments with
+many interfaces, large packet buffers, very high packet rates, or
+memory-constrained systems where you need to limit VPP's memory usage.
+
+**Physmem independent of main heap size** — physmem is for packet
+buffers, main heap is for routing tables.
+
+:::{seealso}
+- {ref}`Hugepages in VyOS Configuration for VPP <vpp-config-hugepages>`
+- {ref}`VPP Buffer Configuration <vpp-config-dataplane-buffers>` - for
+  controlling buffer allocation within physmem
+:::
+
+### Common configurations
+
+```none
+# Reduce for memory-constrained systems
+set vpp settings physmem max-size 4G
+
+# Increase for high-throughput environments
+set vpp settings physmem max-size 32G
+```
+
+## Stats Memory Configuration
+
+VPP uses a dedicated statistics memory segment to store runtime
+counters and telemetry data. This segment is used by the VPP CLI and
+monitoring tools to access performance and status information.
+
+The statistics segment is allocated from hugepage memory and can be
+configured independently from the main heap and physmem settings.
+
+You can configure statistics memory using the following commands:
+
+```{cfgcmd} set vpp settings resource-allocation memory stats page-size \<size\>
+```
+
+Sets the hugepage page size used for the statistics memory segment.
+
+```{cfgcmd} set vpp settings resource-allocation memory stats size \<size\>
+```
+
+Sets the total size of the statistics memory segment.
+
+Increasing this value may be required in large deployments with many
+interfaces or enabled features that generate a high number of counters.
+
+Statistics memory is used only for telemetry and monitoring. It does
+not affect packet buffer allocation or routing table memory.
+
+## Troubleshooting
+
+Improper configuration of main heap size can lead to performance
+degradation or even system instability. If VPP runs out of memory in the
+main heap, it may crash or exhibit erratic behavior. Symptoms you may
+observe include:
+
+- Increased latency or packet loss
+- Crashes or restarts of VPP processes, especially during routing table
+  population (for example, BGP session establishment)
+- Error messages related to memory allocation failures
+
+You need to tune the main heap size based on expected FIB entries. Pay
+attention: the same amount of routes with a single next-hop and with
+multiple next-hops will consume different amounts of memory.
+
+For physmem, insufficient allocation can lead to packet drops, interface
+initialization failures, and overall degraded performance. Symptoms
+include:
+
+- Packet drops or failures to allocate buffers
+- Increased latency or jitter in packet processing
+- Crashes or restarts of VPP processes under heavy load
+
+You need to tune the physmem settings based on expected traffic patterns
+and interface usage. Monitor memory usage closely and adjust the
+configuration as needed to ensure optimal performance.