Encodes the production config, fixed corpus slices, repeat/median discipline
and the noise floor, so the measurement method does not have to be
rediscovered each time. Runs the corpus prefill test through llama-server and
the llama-bench sweep as a controlled cross-check, with interleaved A/B.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PZz44SLQvTXMyWGio6t9DZ
The tiled-transpose fast path in ggml_vk_concat is a large prefill win but a
loss at decode. On a hybrid model like Qwen3.6-35B (gated delta-net on 30 of
40 layers) build_conv_state emits a transposed concat per recurrent layer, so
the fast path runs 30 times per decoded token.
At one token the transposed source is a single column, so there is no
uncoalesced stride left to fix, but the path still costs two dispatches and an
unconditional ggml_vk_sync_buffers - a full pipeline barrier that serializes
the command stream. Measured -17% tg256 on RX 580; the barrier, not the
half-empty transpose dispatch, is nearly all of it.
Require the transposed source to be at least one TILE_DIM wide. That source is
qkv_mixed transposed, so ne[0] is the ubatch token count: prefill keeps the
fast path, decode and small speculative drafts take the generic one.
pp8192 +11% retained, tg256 back to parity, generation byte-identical.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PZz44SLQvTXMyWGio6t9DZ
The vision encoder sits idle in VRAM on every text request. With
LLAMA_MMPROJ_ONDEMAND=1 the server keeps the encoder in RAM (released
after load) and brings it into VRAM just-in-time before mtmd_batch_encode,
releasing it again afterwards - so the encoder's VRAM is free for KV /
expert cache on the common text-only path.
When the encoder does not fit (that VRAM has been claimed), evict the LLM
backbone weights first: they are not needed while the encoder runs (the
decode that uses them happens afterwards), their host shadow is read-only
(cheap free, no D2H), and the KV / prompt cache is left untouched. Order
on the way back matters: free the encoder before re-uploading the weights
so the peak stays within VRAM.
Also wire the encoder release/restore into the VRAM arbiter: vram_go_cold
releases it; the just-in-time encode-path restore replaces the previous
restore in vram_ensure_warm.
Assisted-by: Claude
Add clip_release_device/clip_restore_device (and mtmd_release_device/
mtmd_restore_device wrappers over the vision + audio contexts) that free
the multimodal encoder's device weight buffer to a read-only host shadow
and rebuild it on demand, using the same shadow/free/reallocate pattern
as llama_model weights. No-op for a CPU-backed encoder. This lets the
server drop the ~hundreds-of-MiB vision encoder from VRAM when it is not
encoding an image.
Assisted-by: Claude
On device release with KV eviction, also call ggml_backend_free_scratch()
on each backend so a cold model drops its Vulkan compute preallocations
(reallocated lazily on the next compute via restore).
Also guard llama_context::memory_breakdown() against a freed scheduler:
evict_kv release resets sched to null, so a cold model that is then torn
down (e.g. terminated by the process manager) hit GGML_ASSERT(sched) in
ggml_backend_sched_get_buffer_type. Skip the compute-buffer accounting
when sched is null.
Assisted-by: Claude
Add an optional backend interface method free_scratch (with a public
ggml_backend_free_scratch wrapper) that frees transient/scratch device
memory a backend holds outside of any allocated buffer, keeping the
backend usable - the scratch is reallocated lazily on the next compute.
Implement it for the Vulkan backend (ggml_backend_vk_free_scratch): free
the prealloc_x/y/split_k/add_rms_partials and sync_staging device buffers
and reset their sizes, so an idle/cold model does not hold the vision or
matmul compute preallocations in VRAM. All other backends leave the hook
null (no-op).
Assisted-by: Claude
The recurrent (SSM/conv) state of hybrid models (e.g. Qwen3.5) was left
resident when a model's device buffers were released for on-demand VRAM
sharing - llama_memory_recurrent::release_device_buffers() was a no-op
default. Implement it (and restore_device_buffers) with the same
capture-host-shadow / free / reallocate pattern as llama_kv_cache, so
llama_memory_hybrid now evicts both its attention KV and its recurrent
state. The state is read-write, so its shadow is recaptured on every
release.
Assisted-by: Claude
Under LLAMA_SLEEP_EVICT_KV a cold model still held the scheduler's worst-case
compute buffer (hundreds of MiB, e.g. ~700 MiB for gemma-26B) plus the resident
experts. release_device(evict_kv) now also frees the sched (sched.reset() +
sched_need_reserve), and restore_device() rebuilds it via sched_reserve(), so a
fully-evicted model holds essentially no VRAM (gemma cold: 7147 -> 51 MiB).
Trades a heavier re-warm (weights+KV H2D + sched reserve) for the freed VRAM;
weights-only mode is unchanged (fast switch, keeps KV+compute).
Assisted-by: Claude
With LLAMA_SLEEP_EVICT_KV the KV cache device buffers are freed when a model
goes cold. update_slots() touches the KV before the decode-time vram_ensure_warm
(e.g. SWA models create a checkpoint that reads the KV via ggml_backend_tensor_get),
so the KV must already be resident by then. Move the restore to the sleep-wake
handler (handle_sleeping_state(false)), which runs before update_slots, fixing a
GGML_ASSERT(buffer) crash on iSWA models (gemma) when KV eviction is enabled.
Assisted-by: Claude
release_device_weights()/release_device_buffers() leave a null buffer in
ctxs_bufs while the device memory is released for on-demand VRAM sharing.
The memory-breakdown / total_size / clear paths iterated these and called
ggml_backend_buffer_get_size()/get_type()/clear() on the null buffer, tripping
GGML_ASSERT(buffer) and aborting on shutdown of a cold model. Skip null buffers
in llama_model::memory_breakdown and llama_kv_cache::{memory_breakdown,
total_size,clear}.
Assisted-by: Claude
Before uploading a model's weights, acquire the shared VRAM token (ring the
doorbell so any resident model releases first). Previously load uploaded weights
to VRAM before the arbiter was active, so loading a large model while another
(e.g. the warm 4B task model) held VRAM could exceed the budget and OOM.
- add vram_arena_open() (idempotent flock/doorbell setup) and
vram_acquire_for_load(), called from load_model() before
common_init_from_params().
- a coordinated load now stays warm holding the token and serves its first
request without a re-warm (drop the init-time go_cold cold-start).
Assisted-by: Claude
The request handler only calls wait_until_no_sleep() (which wakes a server out
of its sleeping state) when sleep_idle_seconds >= 0. But the VRAM arbiter's
cross-process doorbell can put a server to sleep even when idle-sleep is
disabled, so without this a doorbell-slept server would never wake and requests
to it would hang until timeout.
Do not bypass the wake path when LLAMA_SLEEP_VRAM_ONLY is set, so the arbiter no
longer depends on --sleep-idle-seconds being configured.
Assisted-by: Claude
Extend on-demand device residency to the KV cache so that when a model's KV
plus another model would not fit in VRAM, the KV can also be evicted to a host
shadow (D2H on release, H2D on restore) instead of only the weights.
- llama_memory_i: add release_device_buffers()/restore_device_buffers()
(default no-op). Implemented in llama_kv_cache (D2H shadow of the live
ctxs_bufs, freed and reallocated like the weights); llama_memory_hybrid and
llama_kv_cache_iswa delegate to their child caches.
- llama_context::release_device(evict_kv): also evict the memory's device
buffers when requested; restore_device() rebuilds them. Public API
llama_context_release_device gains an evict_kv flag.
- server: LLAMA_SLEEP_EVICT_KV=1 enables it. Off by default (weights-only),
since the KV shadow adds a D2H/H2D copy of the live cache each cycle.
Validated on RX 580 (Vulkan), 4B @ 32k ctx: weights-only cold VRAM 1750 MB
(KV stays); weights+KV cold VRAM 726 MB (KV freed, ~1 GB reclaimed). KV
survives the round-trip: prompt cache reused after the cycle (prompt_n 4 vs
42), correct output.
Assisted-by: Claude
Add release/restore of a model's GPU weight buffers (keeping a host shadow
and the KV cache) so several always-loaded llama-server processes can
time-share a single GPU without reloading or losing the prompt cache.
- llama-model: release_device_weights()/restore_device_weights() capture a
compact host shadow (stable iteration order, view-skipping) and free then
realloc the device weight buffers; weights_resident() query.
- llama-context: release_device()/restore_device() wrappers; decode() auto-
restores; public C API llama_context_release_device/restore_device.
- server: LLAMA_SLEEP_VRAM_ONLY makes idle-sleep release only the VRAM weights
(not a full unload/reload). A cross-process flock token in LLAMA_VRAM_ARENA
enforces "resident iff holds token"; an inotify doorbell forces the holder
to release on contention. The warden thread only touches the task queue, so
releases run on the loop thread and never race a decode.
Validated on RX 580 (Vulkan): two models share 8GB, never both resident,
correct output under contention, KV cache preserved (no re-prefill).
Assisted-by: Claude
The generic concat shader reads a transposed source (nb[1]==type_size) with an
uncoalesced stride, which is catastrophically slow on discrete GPUs (~5.6ms for
a 16MB concat on the RX 580 vs ~130us of memory bandwidth), a ~9% prefill
hotspot on Qwen3.5-4B (delta-net state concat).
Add a fast path for concat along dim 0 where one source is stored transposed and
the other source + dst are contiguous along dim 0: copy the contiguous source
with copy.comp and transpose the other source into the matching dst sub-region
with the existing tiled copy_transpose shader (shared-memory 32x32 transpose,
coalesced read+write). Reuses pipeline_cpy_* / pipeline_cpy_transpose_* with
custom push constants + doffset, no new shader. Falls back to the generic path
otherwise (gated on type/shape/contiguity + 16-bit doffset bound).
Assisted-by: opencode
Staging K/V through shared memory looks like an obvious win on GCN: without it
each rowgroup re-reads the whole K/V block from global memory, and with row_split
4 that pulls one 16KB block through a 16KB vector L1 four times.
Measured, it loses: -6.7% pp2048 at depth 16k and -7.4% at 32k on Polaris at head
size 128. The kvsh stride of D/4+1 dwords is 4 mod 32, which costs an 8-way LDS
bank conflict on wave64 - the +1 padding is tuned for warp32 - and the extra
shared memory eats occupancy this shader is already short of.
Comment only, no behaviour change. Leaving a note so the next person does not
spend a GPU on it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
mask_opt was disabled on AMD GCN for head sizes <= 256, but it is
beneficial there in high-context prefill: on fully-visible causal
blocks it skips the per-block mask load+add, and it skips fully-masked
blocks entirely. The attention op on GCN is compute-bound on the
softmax path (no matrix cores), so this cuts real work.
Verified lossless (perplexity bit-identical with it on vs off) and a
measured prefill win on Qwen3.5-35B-A3B (head_dim 256) on an RX 580:
pp2048 unchanged at short context, +8% @ 16k, +12% @ 32k, growing with
depth. Enable for GCN when HSK/HSV >= 256; the existing large-mask
conditions keep it off for decode.
Assisted-by: Claude
Offloaded expert weights are uploaded per split, and to decide which experts to
upload the scheduler reads the routing ids back to the host. The ids are produced
on the same device we are about to upload to, so the readback forces a full
pipeline flush - 47 of them per eval on a 48-layer MoE.
Once the batch draws enough experts the readback stops telling us anything. At
2048 tokens x 10 experts over 256 experts every expert comes back used, so the
bitset is all ones and the copy is a single whole-tensor range anyway.
Skip the readback when the batch guarantees that. Uploading an expert that no id
selects cannot change the result, since mul_mat_id only reads the rows the ids
point at, so this stays exact. Decode is unaffected: n_ids there is the number of
experts per token, far below the threshold, so it keeps the bitset path.
Measured on an RX 580 (Vulkan, Polaris) running Laguna-S-2.1 118B IQ2_M with all
experts host-resident: pp2048 +4.7% at depth 32k, +0.9% at 16k, tg32 +3%.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
LumpiastyandClaude Opus 5