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vulkan: enable coopmat2 FA gqa and split_k optimizations more often #12931

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Merged
merged 1 commit into from
Apr 16, 2025
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vulkan: enable coopmat2 FA gqa and split_k optimizations more often #12931

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6 changes: 3 additions & 3 deletions ggml/src/ggml-vulkan/ggml-vulkan.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5531,7 +5531,7 @@ static void ggml_vk_flash_attn(ggml_backend_vk_context * ctx, vk_context& subctx
uint32_t workgroups_y = (uint32_t)neq2;
uint32_t workgroups_z = (uint32_t)neq3;

if (N == 1 && qk_ratio > 1 && is_pow2(qk_ratio) && gqa_ratio <= flash_attention_num_small_rows &&
if (N == 1 && qk_ratio > 1 && gqa_ratio <= flash_attention_num_small_rows &&
qk_ratio * nek2 == neq2 && nek2 == nev2 && neq3 == 1 && nek3 == 1 && nev3 == 1) {
// grouped query attention - make the N dimension equal to gqa_ratio, reduce
// workgroups proportionally in y dimension. The shader will detect gqa_ratio > 1
Expand All @@ -5544,8 +5544,8 @@ static void ggml_vk_flash_attn(ggml_backend_vk_context * ctx, vk_context& subctx
uint32_t split_kv = KV;
uint32_t split_k = 1;

if (gqa_ratio > 1 && ctx->device->shader_core_count > 0) {
GGML_ASSERT(workgroups_x == 1);
// Try to use split_k when KV is large enough to be worth the overhead
if (workgroups_x == 1 && ctx->device->shader_core_count > 0 && KV >= 512) {
// Try to run two workgroups per SM.
split_k = ctx->device->shader_core_count * 2 / workgroups_y;
if (split_k > 1) {
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2 changes: 1 addition & 1 deletion ggml/src/ggml-vulkan/vulkan-shaders/flash_attn_cm2.comp
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Expand Up @@ -131,7 +131,7 @@ ACC_TYPE perElemOpStoreCol0(const in uint32_t r, const in uint32_t c, const in A
// Load the slope matrix, indexed by Q's dimension 2.
ACC_TYPE perElemOpComputeSlope(const in uint32_t r, const in uint32_t c, const in ACC_TYPE elem, const in uint32_t iq2)
{
const uint32_t h = iq2 + (r & (p.gqa_ratio - 1));
const uint32_t h = iq2 + (r % p.gqa_ratio);

const ACC_TYPE base = ACC_TYPE(h < p.n_head_log2 ? p.m0 : p.m1);
const int exph = int(h < p.n_head_log2 ? h + 1 : 2*(h - p.n_head_log2) + 1);
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4 changes: 3 additions & 1 deletion tests/test-backend-ops.cpp
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Expand Up @@ -4532,7 +4532,9 @@ static std::vector<std::unique_ptr<test_case>> make_test_cases_perf() {

for (int kv : { 4096, 8192, 16384, }) {
for (int hs : { 64, 128, }) {
test_cases.emplace_back(new test_flash_attn_ext(hs, hs, 8, 4, kv, 1, true, 0, 0, GGML_PREC_F32, GGML_TYPE_F16));
for (int nr : { 1, 4, }) {
test_cases.emplace_back(new test_flash_attn_ext(hs, hs, 8, nr, kv, 1, true, 0, 0, GGML_PREC_F32, GGML_TYPE_F16));
}
}
}

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