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phraser: cap llama-server's prompt cache at 512 MiB (V-499)

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The forwarded log named the cause in one line: the prompt cache limit
defaults to 8192 MiB. llama-server saves the full KV state of every idle
slot it evicts, 112 kiB per token, so RSS climbed about 170MB per
distinct prompt until the deployed server held 7.9GB for a 1.1GB model.

Measured on homesrv today, uncapped versus `--cache-ram 512`: RSS
plateaus at 932MB from the fourth distinct prompt instead of climbing.
The task's leading guess was wrong. `-ngl 99` costs almost no RSS,
because RADV keeps device memory outside the process. Numbers and method
in docs/evals/2026-08-03-llama-prompt-cache.md.

`-c 4096` is untouched. The knob is `phraser.cache_ram_mib`, unset means
512, negative passes no flag for a llama-server too old to know it.

The deploy still runs the old image, so the box keeps its 8 GiB default
until mavend is rebuilt.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
claude
2026-08-03 23:19:15 +04:00
parent f229795cea
commit f9b2391a8b
5 changed files with 103 additions and 1 deletions
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cmd/mavend/main.go
+18
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@@ -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 {