From a0ebfdd661a2ccb2700b0e36cfc10ca1a2b4de98 Mon Sep 17 00:00:00 2001 From: Kawrakow Date: Wed, 19 Feb 2025 11:47:07 +0200 Subject: Q8_KV: 8-bit quantization type targeting the KV cache (#208) * Adding q8_KV - Basics + AVX2 gemm/gemv * q8_KV: Better AVX2 gemm * q8_KV: Better Zen4 gemm We get 225.7 t/s for L3-8B. In comparison q8_0 without run-tinme-repacking is at 169 t/s. * q8_KV: AVX2 gemm/gemv We get 254 t/s for L3-8B vs 194 t/s for q8_0 without rtr. * q8_KV: be able to use it for K cache This required quite a few fixes in ggml and llama.cpp: * ggml: do not calculate row size as n/block_size*type_size. I had removed most of it when implementing the quants with per row scale, bit it was stull lurking in ggml_copy. Not sure if these were the last remnants of ggmil-style row sizes, or if there are still places left * llama.cpp: get rid of the the 1d K cache assumption. Create and manage the K-cache as a 2D tensor so we can have per row meta data as needed by q8_KV. Using q8_KV for K-cache results in non-negligible performance gains. More details to follow, but for DeepSeek-Lite with MLA, we get 18% speedup for PP-8192 compared to q8_0 K-cache. * q8_KV: be able to use it for K cache in FA * q8_KV: repack it for K*Q in FA * q8_KV: slightly faster gemv on Zen4 * q8_KV: slightly faster gemv on Zen4 * q8_KV: ARM_NEON We get PP-512 = 167 t/s for L3-8B without interleaving! We do the interleaving on the fly, so I wonder if this could be done for other quants as well. * q8_KV: use it in FA on NEON * q8_KV_r8 - repacked q8_KV On Zen4 it is slower than q8_k_r8 (292 vs 370 t/s) This makes no sense whatsoever as the q8_KV_r8 GEMM is basically the q8_k_r8 GEMM with the unnecessary block stuff removed (so, one would think that it would be faster). * q8_KV_r8: don't use nrc_y = 16 on Zen4 This is faster - 350 t/s. Why? Much better than the 290 t/s we had before, but still slower than the 370 t/s for q8_k_r8. * q8_KV: nrc_y = 16 also doesn't pay off in FA * Minor --------- Co-authored-by: Iwan Kawrakow --- examples/llama-bench/llama-bench.cpp | 3 +++ 1 file changed, 3 insertions(+) (limited to 'examples/llama-bench/llama-bench.cpp') diff --git a/examples/llama-bench/llama-bench.cpp b/examples/llama-bench/llama-bench.cpp index 95df06dc..0222c213 100644 --- a/examples/llama-bench/llama-bench.cpp +++ b/examples/llama-bench/llama-bench.cpp @@ -339,6 +339,9 @@ static ggml_type ggml_type_from_name(const std::string & s) { if (s == "q6_0") { return GGML_TYPE_Q6_0; } + if (s == "q8_KV") { + return GGML_TYPE_Q8_KV; + } return GGML_TYPE_COUNT; } -- cgit v1.2.3