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refactor: adopt FA2-style KernelTraits + compile-time causal/mask dispatch

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- Introduce KernelTraits<HEAD_DIM, BC, WARPS, STAGES> compile-time config bundle, replacing scattered <KD, NC8, KT2, ...> template params
- Template all MMA and scalar kernels on IsCausal/HasMask bools to eliminate inner-loop runtime branches
- Dispatch to 4-path IsCausal/HasMask kernel variants at entry points based on p.causal_offset and p.use_mask
- Update standalone test files with new kernel signatures, add causal test cases
- Fix duplicate using bf16 in MMA kernels that include attn_mma_utils.cuh
This commit is contained in:
ViperEkura
2026-07-21 21:52:46 +08:00
parent ccf728a1b7
commit a01e8bbe98
13 changed files with 682 additions and 611 deletions
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csrc/kernels/attn_paged_decode.cu
+39 -15
View File
@@ -5,6 +5,27 @@
#include "attn_entry_utils.cuh"
#ifndef ASTRAI_NO_MMA
template <int HEAD_DIM, int BC, int STAGES, bool IsCausal, bool HasMask>
static void launch_paged_mma_decode_impl(PagedAttentionParams<bf16>& p) {
using Traits = KernelTraits<HEAD_DIM, BC, 1, STAGES>;
int tiles_total = (p.kv_len + BC - 1) / BC;
p.num_splits = compute_num_splits(p.batch * p.kv_head, tiles_total);
alloc_split_partials(p);
paged_attn_decode_split_kv_mma_kernel<Traits, IsCausal, HasMask>
<<<dim3(p.kv_head, p.batch, p.num_splits), 32>>>(p);
paged_attn_decode_combine_kernel<<<p.batch * p.q_head, p.head_dim>>>(p);
}
template <int HEAD_DIM, int BC, bool IsCausal, bool HasMask>
static void launch_paged_mma_decode(PagedAttentionParams<bf16>& p) {
constexpr int STAGES = (HEAD_DIM <= 128) ? 2 : 1;
launch_paged_mma_decode_impl<HEAD_DIM, BC, STAGES, IsCausal, HasMask>(p);
}
#endif
template <int HEAD_DIM, bool IsCausal, bool HasMask>
static void launch_paged_scalar_decode(PagedAttentionParams<bf16>& p) {
int group_size = p.q_head / p.kv_head;
int chunks_total = (p.kv_len + PDC_CHUNK - 1) / PDC_CHUNK;
@@ -14,32 +35,35 @@ static void launch_paged_scalar_decode(PagedAttentionParams<bf16>& p) {
size_t smem = PDC_CHUNK * p.head_dim * sizeof(bf16);
dim3 grid = dim3(p.batch * p.kv_head, 1, p.num_splits);
dim3 block = dim3(32, group_size);
paged_attn_decode_split_kv_kernel<<<grid, block, smem>>>(p);
paged_attn_decode_split_kv_kernel<HEAD_DIM, IsCausal, HasMask><<<grid, block, smem>>>(p);
paged_attn_decode_combine_kernel<<<p.batch * p.q_head, p.head_dim>>>(p);
}
#ifndef ASTRAI_NO_MMA
template <int HEAD_DIM, int BC, int STAGES = (HEAD_DIM <= 128) ? 2 : 1>
static void launch_paged_mma_decode(PagedAttentionParams<bf16>& p) {
int tiles_total = (p.kv_len + BC - 1) / BC;
p.num_splits = compute_num_splits(p.batch * p.kv_head, tiles_total);
alloc_split_partials(p);
paged_attn_decode_split_kv_mma_kernel<HEAD_DIM, BC, STAGES><<<dim3(p.kv_head, p.batch, p.num_splits), 32>>>(p);
paged_attn_decode_combine_kernel<<<p.batch * p.q_head, p.head_dim>>>(p);
}
#endif
template <int HEAD_DIM>
static void dispatch_paged_decode(PagedAttentionParams<bf16>& p) {
bool is_causal = (p.causal_offset >= 0);
bool has_mask = (p.use_mask && p.mask);
#ifndef ASTRAI_NO_MMA
int G = p.q_head / p.kv_head;
if (G >= 1 && G <= 16 && p.page_size >= 32) {
launch_paged_mma_decode<HEAD_DIM, 32>(p);
if (is_causal) {
if (has_mask) launch_paged_mma_decode<HEAD_DIM, 32, true, true>(p);
else launch_paged_mma_decode<HEAD_DIM, 32, true, false>(p);
} else {
if (has_mask) launch_paged_mma_decode<HEAD_DIM, 32, false, true>(p);
else launch_paged_mma_decode<HEAD_DIM, 32, false, false>(p);
}
return;
}
#endif
launch_paged_scalar_decode(p);
if (is_causal) {
if (has_mask) launch_paged_scalar_decode<HEAD_DIM, true, true>(p);
else launch_paged_scalar_decode<HEAD_DIM, true, false>(p);
} else {
if (has_mask) launch_paged_scalar_decode<HEAD_DIM, false, true>(p);
else launch_paged_scalar_decode<HEAD_DIM, false, false>(p);
}
}
torch::Tensor attn_paged_decode(