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See https://github.com/iacopPBK/llama.cpp-gfx906 . AMD GPUs support reads of up to 16 bytes from SRAM. This PR extends the tile FlashAttention CUDA kernel with support for reads of 8 or 16 bytes. The FP32 -> FP16 type conversion is also done prior to writing the data to SRAM to reduce I/O further.

I also checked the AMD ISA documentation for v_dot2_f32_f16 support and adjusted the code paths accordingly; it seems to be available everywhere except for RDNA 1.

Performance changes
GPU Model Microbatch size Test t/s master t/s 5bae9f9 Speedup
MI50 gemma 2B Q4_0 16 pp16384 629.54 716.54 1.14
MI50 gemma 2B Q4_0 32 pp16384 728.28 911.94 1.25
MI50 gemma 2B Q4_0 512 pp16384 1412.40 2141.40 1.52
MI50 llama 1B Q4_0 16 pp16384 927.48 998.83 1.08
MI50 llama 1B Q4_0 32 pp16384 1189.48 1338.73 1.13
MI50 llama 1B Q4_0 512 pp16384 2278.02 2898.30 1.27
MI50 llama 8B Q4_0 16 pp16384 277.56 294.46 1.06
MI50 llama 8B Q4_0 32 pp16384 334.59 366.55 1.10
MI50 llama 8B Q4_0 512 pp16384 508.27 606.21 1.19
RX 6800 gemma 2B Q4_0 16 pp16384 399.91 636.85 1.59
RX 6800 gemma 2B Q4_0 32 pp16384 313.91 992.28 3.16
RX 6800 gemma 2B Q4_0 512 pp16384 568.27 1897.49 3.34
RX 6800 llama 1B Q4_0 16 pp16384 644.87 903.19 1.40
RX 6800 llama 1B Q4_0 32 pp16384 658.72 1336.48 2.03
RX 6800 llama 1B Q4_0 512 pp16384 897.77 2301.67 2.56
RX 6800 llama 8B Q4_0 16 pp16384 172.06 234.54 1.36
RX 6800 llama 8B Q4_0 32 pp16384 174.27 328.20 1.88
RX 6800 llama 8B Q4_0 512 pp16384 231.13 530.74 2.30

@github-actions github-actions bot added Nvidia GPU Issues specific to Nvidia GPUs ggml changes relating to the ggml tensor library for machine learning labels Sep 10, 2025
@JohannesGaessler JohannesGaessler force-pushed the cuda-fa-tile-mem-pattern-4 branch from 4ff6731 to fe4eb4f Compare September 11, 2025 12:00
@JohannesGaessler JohannesGaessler linked an issue Sep 11, 2025 that may be closed by this pull request
} else if constexpr (nbytes == 16) {
*(int4 *) dst = *(const int4 *) src;
} else {
static_assert(nbytes == 0 && nbytes == -1, "bad nbytes");
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Wouldn't this work?

Suggested change
static_assert(nbytes == 0 && nbytes == -1, "bad nbytes");
static_assert(false, "bad nbytes");

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I tried this first, it failed during the host pass.

@JohannesGaessler JohannesGaessler merged commit 0e6ff00 into ggml-org:master Sep 11, 2025
47 of 48 checks passed
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Includes fix for v_dot2_f32_f16 being used on ISAs without that instruction.

ggml-org/llama.cpp#15927
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)"

This reverts commit 75a3a6c.

d

Update cudart64_12.dll

Revert "Cudart 12.9"

This reverts commit f79c687.

Revert "Allow compile exe, pdf features off"

This reverts commit 5e1c154.

Update fattn.cu

Update set-rows.cu

batches

Revert "try fix fattn again, porting some older code. the cc detection is not working well, so its hacky"

This reverts commit 7b04191.

Update ggml-cuda.cu

Update fattn.cu

Update fattn.cu

Update fattn.cu

Add option to disable MMA support on Turing

Author : pt13762104

GGML_CUDA_NO_PEER_COPY to try to fix a crash on Gemma 3

Deactivate SWA when Fast Forwarding, commented

Wrench Fix for the SWA I borked

Clean-up quantkv algo

comment warp sizes for now in IQ_K MMQ Kernels

KV 24 -> KV 31

Add a readme.

ngxson's commented hack

Try some hack for gpt-oss

Update llama-vocab.cpp

Bump Windows max open files from 512 to 2048

Author : Thireus

CLI - Specify GGML_TYPE to quantize for the main tensors. (#91)

To complement the token_embd.weight and output.weight :

attn_v.weight
attn_k.weight.
attn_q_weight
attn_output.weight
attn_qkv.weight
ffn_gate
ffn_down
ffn_up

EsoCroK naming

v1.99430_b6645-6_Q6-IO2346_RMv1.17.99m

Disable I2_K cpu quantization.

To allow compilation.

MMQ code adaptation

Update mmq.cuh

MMQ Initial code for IQ2,3,4,5,6_K

IQ_K quants first gen (4, 5, 6)

Some logs back

Batches

Croco Bench.

Double the anti-abuse limits

Allow compile exe, pdf features off

Revert "Allow compile exe, pdf features off"

This reverts commit 5e2451f129f0bca326f74aae24df475c0410cdbf.

Update koboldcpp.py

Revert "Allow compile exe, pdf features off"

This reverts commit 2a7e9e004e8578a05fb67967d09cf36263867b9b.

Revert "Allow compile exe, pdf features off"

This reverts commit b4fd7809a4f77ff18bd415fcfb2d5f435e3b63a3.

quantization tweaks

iq3_ks quantization tweaks

Minor iq3_k tweak

q2_K tweaks

q3_K tweaks

q4_K tweaks

q5_K tweaks

GGUF v14 attempt of second fix.

loosen gguf restrictions.

Quantization improvements #295 and #302, GGML part only

Improved IQ2_XS quantization #312

Improved IQ1_M quantization #327

ggml_row_size accounting fix for GGUF v14

Credits : @ikawrakow

Fighting with cmake #279

Drop the GGML count limitation limit

Old markings

Customize KCPP.py

Croco additional chat adapters andtemplates

Reinstate "skip barrier of noop"

Allow q8_0 KV cache for head size 256 #330

Up FA KV modes

256 candidates (1024 with Grammar)

Adapt q6_0 MMQ to llama.cpp mainline

Q6_0 MMQ Kernel attempt

MMQ for Q6_0 authored by Ikawrakow

Add Q6_0 MMQ to template generator authored by Ikawrakow

Q6_0 KVQ for KCPP/Croco -> KV22

For release.

fix a few lazy-cuts and hiccups left during the merge of IQ4_NL.

dequantize for q6_0 and related cpy

Enable q6_0 for flash attention

As with IQ4_NL, just for head size of 128 for now. Without GGML_CUDA_FA_ALL_QUANTS set, only Q6_0 + Q5_0 and Q8_0 + Q6_0 are included. With this the VRAM poor have better options for selecting the best possible (as allowed by VRAM, model size, context length) quantized KV-cache.

PR by Ikawrakow on ik_llama.cpp

Adding Q6_0 (#77) Rev 20240807

* Adding q6_0 - basics + AVX2/Zen4 working

* Adding q6_0: CUDA dequantize works, but not mmvq

* Adding q6_0: CUDA mmvq works

* Adding q6_0: CUDA cpy, so Q6_0 can be used for KV-cache

* Add q6_0 to CPU flash attention

Disappointing result: for LlaMA-3.2-1B, q6_0 K- and V-cache
gives about the same PPL as q8_0 K-cache and q4_0 V-cache,
while needing the exact same RAM.
I.e., what was the point?

* q6_0: slightly better kv-cache result

Better than q8_0+q4_0, but not as good as q8_0+iq4_nl

* q6_0: works on ARM_NEON

* q6_0: dequantize works on Metal, but not vector dot product

* q6_0: it now works on Metal

Outperforms q5_0 by a significant margin. E.g.
| model                          |       size |     params | backend    | ngl | threads |          test |              t/s |
| ------------------------------ | ---------: | ---------: | ---------- | --: | ------: | ------------: | ---------------: |
| llama 8B Q6_0                  |   6.08 GiB |     8.03 B | Metal      | 100 |       4 |         tg128 |     44.02 ± 0.08 |
| llama 8B Q5_0                  |   5.21 GiB |     8.03 B | Metal      | 100 |       4 |         tg128 |     40.13 ± 0.12 |
| llama 8B Q6_0                  |   6.08 GiB |     8.03 B | Metal      | 100 |       4 |         pp512 |    500.55 ± 0.32 |
| llama 8B Q5_0                  |   5.21 GiB |     8.03 B | Metal      | 100 |       4 |         pp512 |    448.02 ± 0.27 |

* q6_0: can now be used for kv-cache on Metal -> skipped.

---------

Adaptation to mainline by me!

IQ4_NL KVQ for KCPP/Croco

missing templates instances for KVQ IQ4_NL
Update fattn.cu for KVQ IQ4_NL
Update fattn-vec-f16.cuh for KVQ IQ4_NL
Update fattn-vec-f32.cuh for KVQ IQ4_NL
CML and Makefile FOR IQ4_NL

KV_IQ4_NL uncommenting VEC16 cases
KV_IQ4_NL uncommenting VEC32 cases

Enable IQ4_NL for V-cache in token generation

Add IQ4_NL + IQ4_NL to FA

This is a better alternative than Q4_0 + Q4_0 for the VRAM poor.

Comment unwanted add-in in makefile

iq4_nl: faster quantization (#76)

CUDA: faster float -> iq4_nl conversion (#73)

* iqk_mul_mat: better iq4_nl implementation on Zen4/AVX2

PP-512 performance for LLaMA-3.1-8B goes to 162.6 t/s up
from 133.2 t/s.

Default Blas Batch Size = 128

Quant KV and Draft QKV, 24 modes

With customizable QKV for the draft as well.
And reduced Blas Batch Size for the draft model.

Default Draft Amount = 4

Bench context size

Max contextsize and steps

Croco CML

SCHED_MAX_COPIES = 1

And Croco usual additions to the CMakeList

Cudart 12.9

Revert "CUDA: faster tile FA (Pascal/AMD), headsize 256 (ggml-org#15769)"

This reverts commit 79bc429.

Revert "HIP: use v_dot2_f32_f16 instruction for FA (ggml-org#15884)"

This reverts commit 17bc5a8.

Revert "CUDA: larger SRAM reads for tile FA, AMD FP16 dot (ggml-org#15927)"

This reverts commit 0e6ff00.

Revert "CUDA: fix FA occupancy, optimize tile kernel (ggml-org#15982)"

This reverts commit c959b67.

Revert "CUDA: fix compilation on CC 6.0 (ggml-org#16091)"

This reverts commit 368560a.

Co-Authored-By: Kawrakow <iwankawrakow@gmail.com>
Co-Authored-By: Iwan Kawrakow <iwan.kawrakow@gmail.com>
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Compile bug: Failing to compile with hipblas and gfx803

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