Vulkan Scalar Flash Attention Refactor (#19625)

* vulkan: allow using fp16 in scalar flash attention shader

* split rows inside of subgroups for faster synchronization

* use row_split when Br >= 4, change reductions to use shared memory if row_split == 1

* use f32 scalar FA if f16 is not supported by device

* fix amd workgroup size issue

* optimize masksh use

* add medium rows FA shader Br size

* fixes

* add padding to mask shmem buffer

* cache q values into registers for KQ

* fuse lf accumulation, pf and v accumulation into a loop

* stage K loads through shmem

* stage V loads through shmem

* only stage through shmem on Nvidia

* default to Bc 32

* also stage V through shmem when this is done for K

* dynamic subgroups for intel

* use vectorized stores

* use float_type for dequantize4 functions

* use smaller scalar rows size for smaller rows count

* relax flash attention split_k condition to allow non-gqa use

* use minimal subgroup size on Intel

* fix shmem support function

* fix rebase issues

* fixes

* Bc 4 for scalar FA is not a valid configuration

* Use wave32 on AMD RDNA for scalar FA

* add Intel shader core count lookup-table

* fix regressions

* device tuning

* tmpsh size fix

* fix editorconfig

* refactor fa tuning logic into a single place

* fix gqa opt logic

* fix block_rows with small n_rows

* amd tuning

* fix hsk=72/80 issue

* tuning

* allow condition skipping for column check

* use float16 for Of if available

* address feedback

* fix bad RDNA performance on head size <= 128 by limiting occupancy

* allow printing pipeline stats

* cleanup and fixes

* limit occupancy for GCN for small batch FA with large HSK

* disable f16 FA for GCN AMD GPUs on the proprietary driver
This commit is contained in:
Ruben Ortlam
2026-02-24 08:35:48 +01:00
committed by GitHub
parent 8c2c0108dd
commit aa6f918c1c
6 changed files with 979 additions and 550 deletions
@@ -595,8 +595,6 @@ void matmul_shaders(bool fp16, MatMulIdType matmul_id_type, bool coopmat, bool c
}
void process_shaders() {
std::map<std::string, std::string> base_dict = {{"FLOAT_TYPE", "float"}, {"FLOAT_TYPE_VEC2", "vec2"}};
// matmul
for (const MatMulIdType& matmul_id_type : {MatMulIdType::NONE, MatMulIdType::DEFAULT, MatMulIdType::SUBGROUP}) {
// No coopmats
@@ -622,49 +620,63 @@ void process_shaders() {
}
}
// flash attention
for (const auto& f16acc : {false, true}) {
std::map<std::string, std::string> fa_base_dict = base_dict;
fa_base_dict["ACC_TYPE"] = f16acc ? "float16_t" : "float";
fa_base_dict["ACC_TYPEV4"] = f16acc ? "f16vec4" : "vec4";
if (f16acc) {
fa_base_dict["ACC_TYPE_MAX"] = "float16_t(65504.0)";
for (const bool& fp16 : {false, true}) {
std::map<std::string, std::string> base_dict;
if (fp16) {
base_dict = {{"FLOAT_TYPE", "float16_t"}, {"FLOAT_TYPEV4", "f16vec4"}, {"FLOAT16", "1"}, {"FLOAT_TYPE_MAX", "float16_t(65504.0)"}};
} else {
base_dict = {{"FLOAT_TYPE", "float"}, {"FLOAT_TYPEV4", "vec4"}};
}
for (const auto& tname : type_names) {
if (tname == "bf16") continue;
#if defined(GGML_VULKAN_COOPMAT2_GLSLC_SUPPORT)
if (tname == "f16") {
string_to_spv("flash_attn_f32_f16_" + tname, "flash_attn_cm2.comp",
merge_maps(fa_base_dict, {{"Q_TYPE", "float"}, {"D_TYPE", "float"}}), true, false, true, f16acc);
} else {
std::string data_a_key = "DATA_A_" + to_uppercase(tname);
string_to_spv("flash_attn_f32_f16_" + tname, "flash_attn_cm2.comp",
merge_maps(fa_base_dict, {{data_a_key, "1"}, {"Q_TYPE", "float"}, {"D_TYPE", "float"}, {"DEQUANTFUNC", "dequantFunc"+to_uppercase(tname) }, {"BLOCK_SIZE", "QUANT_K_"+to_uppercase(tname) }}), true, false, true, f16acc);
// flash attention
for (const bool& f16acc : {false, true}) {
std::map<std::string, std::string> fa_base_dict = base_dict;
fa_base_dict["ACC_TYPE"] = fp16 && f16acc ? "float16_t" : "float";
fa_base_dict["ACC_TYPEV4"] = fp16 && f16acc ? "f16vec4" : "vec4";
if (fp16 && f16acc) {
fa_base_dict["ACC_TYPE_MAX"] = "float16_t(65504.0)";
}
for (const auto& tname : type_names) {
if (tname == "bf16") continue;
if (fp16) {
#if defined(GGML_VULKAN_COOPMAT2_GLSLC_SUPPORT)
if (tname == "f16") {
string_to_spv("flash_attn_f32_f16_" + tname, "flash_attn_cm2.comp",
merge_maps(fa_base_dict, {{"Q_TYPE", "float"}, {"D_TYPE", "float"}, {"D_TYPEV4", "vec4"}}), fp16, false, true, f16acc);
} else {
std::string data_a_key = "DATA_A_" + to_uppercase(tname);
string_to_spv("flash_attn_f32_f16_" + tname, "flash_attn_cm2.comp",
merge_maps(fa_base_dict, {{data_a_key, "1"}, {"Q_TYPE", "float"}, {"D_TYPE", "float"}, {"D_TYPEV4", "vec4"}, {"DEQUANTFUNC", "dequantFunc"+to_uppercase(tname) }, {"BLOCK_SIZE", "QUANT_K_"+to_uppercase(tname) }}), fp16, false, true, f16acc);
}
#endif
#if defined(GGML_VULKAN_COOPMAT_GLSLC_SUPPORT)
if (tname == "f16") {
string_to_spv("flash_attn_f32_f16_" + tname, "flash_attn_cm1.comp",
merge_maps(fa_base_dict, {{"Q_TYPE", "float"}, {"D_TYPE", "float"}, {"COOPMAT", "1"}}), true, true, false, f16acc);
} else if (tname == "q4_0" || tname == "q8_0" || tname == "f32") {
std::string data_a_key = "DATA_A_" + to_uppercase(tname);
string_to_spv("flash_attn_f32_f16_" + tname, "flash_attn_cm1.comp",
merge_maps(fa_base_dict, {{data_a_key, "1"}, {"Q_TYPE", "float"}, {"D_TYPE", "float"}, {"BLOCK_SIZE", "QUANT_K_"+to_uppercase(tname)}, {"COOPMAT", "1"}}), true, true, false, f16acc);
}
if (tname == "f16") {
string_to_spv("flash_attn_f32_f16_" + tname, "flash_attn_cm1.comp",
merge_maps(fa_base_dict, {{"Q_TYPE", "float"}, {"D_TYPE", "float"}, {"D_TYPEV4", "vec4"}, {"COOPMAT", "1"}}), fp16, true, false, f16acc);
} else if (tname == "q4_0" || tname == "q8_0" || tname == "f32") {
std::string data_a_key = "DATA_A_" + to_uppercase(tname);
string_to_spv("flash_attn_f32_f16_" + tname, "flash_attn_cm1.comp",
merge_maps(fa_base_dict, {{data_a_key, "1"}, {"Q_TYPE", "float"}, {"D_TYPE", "float"}, {"D_TYPEV4", "vec4"}, {"BLOCK_SIZE", "QUANT_K_"+to_uppercase(tname)}, {"COOPMAT", "1"}}), fp16, true, false, f16acc);
}
#endif
if (tname == "f16") {
string_to_spv("flash_attn_f32_f16_" + tname, "flash_attn.comp",
merge_maps(fa_base_dict, {{"Q_TYPE", "float"}, {"D_TYPE", "float"}}), true, false, false, f16acc);
} else if (tname == "q4_0" || tname == "q8_0" || tname == "f32") {
std::string data_a_key = "DATA_A_" + to_uppercase(tname);
string_to_spv("flash_attn_f32_f16_" + tname, "flash_attn.comp",
merge_maps(fa_base_dict, {{data_a_key, "1"}, {"Q_TYPE", "float"}, {"D_TYPE", "float"}, {"BLOCK_SIZE", "QUANT_K_"+to_uppercase(tname) }}), true, false, false, f16acc);
}
if (tname == "f16") {
string_to_spv("flash_attn_f32_f16_" + tname, "flash_attn.comp",
merge_maps(fa_base_dict, {{"Q_TYPE", "float"}, {"D_TYPE", "float"}, {"D_TYPEV4", "vec4"}}), fp16, false, false, f16acc);
} else if (tname == "q4_0" || tname == "q8_0" || tname == "f32") {
std::string data_a_key = "DATA_A_" + to_uppercase(tname);
string_to_spv("flash_attn_f32_f16_" + tname, "flash_attn.comp",
merge_maps(fa_base_dict, {{data_a_key, "1"}, {"Q_TYPE", "float"}, {"D_TYPE", "float"}, {"D_TYPEV4", "vec4"}, {"BLOCK_SIZE", "QUANT_K_"+to_uppercase(tname) }}), fp16, false, false, f16acc);
}
}
}
}
std::map<std::string, std::string> base_dict = {{"FLOAT_TYPE", "float"}, {"FLOAT_TYPE_VEC2", "vec2"}};
for (const auto& tname : type_names) {
// mul mat vec
std::string data_a_key = "DATA_A_" + to_uppercase(tname);