llama.cpp

be876204 - sycl: bind the f16 KV cache in place for the oneDNN SDPA path (#27468)

sycl: bind the f16 KV cache in place for the oneDNN SDPA path (#27468) Measured at a live KV length of 34816 (32768 depth plus one 2048 ubatch), on Qwen3.8 27B Q4_K_S: per tensor 4 * 34816 * 256 * 2 B = 71.3 MB staged per call K and V, so 2x = 142.6 MB traffic per call read once, write once = 285.2 MB traffic per ubatch 285.2 MB * 16 calls = 4.56 GB One ubatch is one ggml_cgraph submission (llama_context::process_ubatch -> graph_compute), so that 4.56 GB is the cost of a single 2048-token prefill chunk, and it scales with the live KV length: the first ubatch of the same run, at seq = 2048, moves 0.27 GB. Reproduce the two measured inputs with: GGML_SCHED_DEBUG=2 llama-bench -m MODEL -p 8 -n 0 -r 1 -ngl 0 \ -fa on -ctk f16 -ctv f16 -v > nd.txt 2>&1 grep -E 'n_layer|n_head_kv|n_embd_head_k' nd.txt awk '/node # 0 /{g++} g==1 && /\(FLASH_ATTN\)/{n++} END{print n+0}' nd.txt