Add the flash-attn mask_opt change (auto-on for GCN large head sizes,
lossless, +12% pp @ 32k on the RX 580) and correct the earlier pinning
advice: pinning helps in isolated llama-bench but fails in a long-running
server on RADV, so --no-mmap is the serving path. Add a recommended
Polaris serving command.
Assisted-by: Claude
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
Pinning helps on Vulkan too, but GGML_SCHED_PREFETCH_EXPERTS regresses
there (second backend shares one device queue, no overlap). Add an RX 580
Polaris benchmark and the context-dependent --n-cpu-moe guidance.
Assisted-by: Claude
Pinned async host uploads can record into compute_ctx before graph
compute, so the perf logger's opening timestamp must append after them
instead of asserting the context is expired. Without this, profiling
(GGML_VK_PERF_LOGGER) crashes whenever host-register pinning is on.
Assisted-by: Claude
VK_EXT_external_memory_host import fails on RADV for file-backed mmap pages,
so register_host_buffer no-op'd and every MoE-expert upload paid a slow
single-threaded pageable memcpy into the staging buffer each eval (~3 GB/s
effective on the 35B, ~25% of PCIe bandwidth).
When the import fails, fall back to a one-time copy of the region into a
host-visible Vulkan buffer registered in device->pinned_memory under the
mmap's address range. The existing pinned fast path then DMAs straight from
that buffer each eval at full PCIe bandwidth - no per-eval CPU memcpy and no
blocking sync. Costs one-time host-visible memory equal to the CPU-resident
weight region.
Assisted-by: opencode
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
Export register_host_buffer/unregister via the backend reg so the existing
GGML_CUDA_REGISTER_HOST path in llama-model-loader pins mmap'd expert
weights on Vulkan. Imports host pages through VK_EXT_external_memory_host
into device->pinned_memory, letting the existing pinned fast path in
ggml_vk_buffer_write_2d_async DMA straight from system RAM instead of
bouncing through the staging buffer + blocking host memcpy.
A single Vulkan buffer cannot cover a multi-GB mmap (capped at
device->max_buffer_size), so the region is imported in page-aligned
chunks; a bound check makes tensors straddling a chunk boundary fall back
to staging instead of reading out of bounds. Opt-in via
GGML_CUDA_REGISTER_HOST=1 or GGML_VK_REGISTER_HOST=1, no-op otherwise.
Assisted-by: opencode
Lumpiasty