cmd/mavend/main.go

@@ -251,6 +251,7 @@ func run(args []string) error {
 				Listen:       cfg.Phraser.Listen,
 				NGpuLayers:   cfg.Phraser.NGpuLayers,
 				NCtx:         cfg.Phraser.NCtx,
+				CacheRAMMiB:  cacheRAMMiB(cfg.Phraser.CacheRAMMiB),
 				Timeout:      time.Duration(cfg.Phraser.Timeout),
 				LLMNudges:    cfg.Phraser.LLMNudges,
 				ContextBlock: contextBlockFn(cfg, time.Now),
@@ -525,6 +526,7 @@ func run(args []string) error {
 					Listen:       cfg.Phraser.Listen,
 					NGpuLayers:   cfg.Phraser.NGpuLayers,
 					NCtx:         cfg.Phraser.NCtx,
+					CacheRAMMiB:  cacheRAMMiB(cfg.Phraser.CacheRAMMiB),
 					Timeout:      time.Duration(cfg.Phraser.Timeout),
 					LLMNudges:    cfg.Phraser.LLMNudges,
 					ContextBlock: contextBlockFn(cfg, time.Now),
@@ -788,6 +790,22 @@ func personaFacts(cfg *config.Config) persona.Facts {
 	return f
 }
 
+// cacheRAMMiB resolves phraser.cache_ram_mib into the phraser's field. Unset
+// means 512 MiB and not "whatever the server does", because the server's own
+// default is 8 GiB of prompt cache and that is what put 7.9 GB of RSS and half
+// a gigabyte of swap on homesrv for a 1.1 GB model. A negative value is the
+// deliberate opt-out: no flag is passed, the server's default applies, and the
+// operator owns the consequence.
+func cacheRAMMiB(configured int) int {
+	if configured == 0 {
+		return 512
+	}
+	if configured < 0 {
+		return 0
+	}
+	return configured
+}
+
 // contextBlockFn returns the per-turn renderer of the shared context block.
 // Per turn, not once at startup, because the block states the current time.
 func contextBlockFn(cfg *config.Config, now func() time.Time) func() string {

deploy/mavend.json

@@ -20,6 +20,7 @@
     "bin_path": "llama-server",
     "n_gpu_layers": 99,
     "n_ctx": 4096,
+    "cache_ram_mib": 512,
     "timeout": "60s",
     "llm_nudges": false
   },

docs/evals/2026-08-03-llama-prompt-cache.md

@@ -0,0 +1,77 @@
+# Where the resident model's 7.9GB of RSS goes (2026-08-03, homesrv)
+
+Measured for Vikunja #499. The deployed llama-server held 7.9GB RSS for a 1.1GB
+model file. Half a gigabyte of it was in swap, on a box that also runs
+whisper.cpp, piper and the embedder.
+
+## Method
+
+`maven-mavend-1` was stopped for the measurement, with the owner's approval.
+Its own binary then ran on the host with the exact deployed command line. That
+binary is `/opt/maven/bin/llama-server`, version `1 (4c65955)`, a Vulkan build.
+
+```sh
+llama-server -m /mnt/hdd1/llms/qwen3/Qwen3-1.7B-UD-Q4_K_XL.gguf \
+  --host 127.0.0.1 --port 18099 -c 4096 -ngl 99 --no-webui
+```
+
+RSS was read from `/proc/<pid>/status` after load and after each of 8 distinct
+1521-token prompts. `smaps` of the deployed process was read first, from inside
+the container, since the host user cannot read another user's maps.
+
+## The cause: the prompt cache, not the weights and not the offload
+
+The startup log says it outright:
+
+```text
+srv load_model: prompt cache is enabled, size limit: 8192 MiB
+srv llama_server: n_parallel is set to auto, using n_parallel = 4 and kv_unified = true
+```
+
+The server saves the full KV state of every idle slot it evicts. It keeps up to
+8GiB of those states in host RAM (llama.cpp PR 16391). One saved prompt of 1521
+tokens costs 166.377 MiB. That is 112 kiB per token, exactly Qwen3-1.7B's KV
+footprint (28 layers x 2 x 1024 dims x 2 bytes).
+
+RSS at rest, and per distinct prompt:
+
+| Prompts served | RSS, default | RSS, `--cache-ram 512` |
+|---|---|---|
+| 0 (just loaded) | 443 MB | 411 MB |
+| 1 | 445 MB | 411 MB |
+| 4 | 958 MB | 929 MB |
+| 8 | 1641 MB | 932 MB |
+
+Uncapped, RSS climbs about 170MB per distinct prompt and does not stop until
+the 8GiB limit. Capped at 512 MiB it plateaus at 932MB from the fourth prompt
+on, with the cache holding steady at `3 prompts, 499.132 MiB` and evicting.
+
+The 7.9GB on the running daemon was that climb, weeks of it. Its `smaps` showed
+one 6.03GB anonymous mapping at 5.32GB resident plus a 1.45GB mapping at 1.27GB
+resident, and only 30MB of file-backed RSS.
+
+## The task's leading guess was wrong
+
+`-ngl 99` on the Vega iGPU costs almost no process RSS. A freshly loaded server
+has 95MB of anonymous RSS in total. RADV allocates device memory through the
+kernel, outside the process, and the log sees 8202 MiB free on `Vulkan0`. The
+weights are mmapped and file-backed, so they are evictable and do not pin RSS. The logit buffer is not visible in the numbers above at all.
+
+## Decision
+
+`--cache-ram 512` is now the default, wired as `phraser.cache_ram_mib` and set
+in `deploy/mavend.json`. 512 MiB caps total RSS near 1GB, an eighth of what the
+box carried. It still holds three of the 1521-token probes above. Maven's real
+routing and phrasing prompts are much shorter, so it holds more of those than
+the table suggests. `-c 4096` is untouched, as #499
+required. A negative `cache_ram_mib` passes no flag, for a llama-server too old
+to know it.
+
+Not changed: `n_parallel = 4`. With `kv_unified = true` the four slots share one
+4096-token KV cache, so they do not multiply it.
+
+The other half of #499 was that none of these lines were reachable. mavend
+scraped llama-server's stderr for the listen line and discarded it, and never
+piped stdout at all. Both streams now go to mavend's log with a `llama:` prefix.
+The last 12 startup lines go into the error when the server dies before it
+listens.

internal/config/config.go

@@ -1276,6 +1276,12 @@ type PhraserConfig struct {
 	NCtx       int      `json:"n_ctx,omitempty"`
 	Timeout    Duration `json:"timeout,omitempty"`
 
+	// CacheRAMMiB bounds llama-server's prompt cache. Omitted ⇒ 512 MiB, which
+	// is what keeps the resident model near 1 GB of RSS instead of the 7.9 GB
+	// measured on 2026-08-03. Set it to -1 to pass no flag at all and let the
+	// server apply its own 8 GiB default. See phraser.Config.CacheRAMMiB.
+	CacheRAMMiB int `json:"cache_ram_mib,omitempty"`
+
 	// LLMNudges — let the model word nudges again. Off by default: nudges are
 	// worded from hand-written Russian templates now (the model broke the
 	// persona and invented units). Chat, query and reminder phrasing always go

internal/phraser/llmphraser.go

@@ -133,7 +133,7 @@ func DefaultConfig(modelPath string) Config {
 		NCtx:       2048,
 		// 512 MiB caps total RSS near 1 GB and still holds several recent prompts.
 		CacheRAMMiB: 512,
-		Timeout:    30 * time.Second,
+		Timeout:     30 * time.Second,
 	}
 }