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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/tests/attn_decode_test.cu
+109 -80
View File
@@ -1,5 +1,5 @@
/*
Pure-C test:
Pure-C test — updated for KernelTraits + IsCausal/HasMask.
nvcc -I csrc -arch=sm_89 -O3 \
--use_fast_math --ptxas-options=-O3 --extra-device-vectorization \
csrc/tests/attn_decode_test.cu -o test && ./test
@@ -11,35 +11,29 @@ nvcc -I csrc -arch=sm_89 -O3 \
#include "../kernels/attn_decode_split_kv_mma.cuh"
#endif
// Split-K scratch (torch-free): the production launcher allocates these from
// torch; here we pass pre-allocated device buffers so the bench loop doesn't
// pay a cudaMalloc per iteration. Size for the maximum split count (32).
// Split-K scratch (torch-free)
struct DecodeScratch {
float* o_part = nullptr;
float* ml_part = nullptr;
};
// Launch the production decode path (tensor-core head-packing MMA on sm_80+,
// scalar fallback otherwise), mirroring dispatch_decode() in attn_decode.cu.
#ifndef ASTRAI_NO_MMA
static bool decode_use_mma(const AttentionParams<bf16>& p) {
int G = p.q_head / p.kv_head;
return !p.use_mask && G > 1 && G <= 16;
}
template <int HEAD_DIM, int BC, int STAGES = (HEAD_DIM <= 128) ? 2 : 1>
template <int HEAD_DIM, int BC, bool IsCausal, bool HasMask>
static void launch_mma_decode(AttentionParams<bf16>& p, DecodeScratch& sc) {
constexpr int STAGES = (HEAD_DIM <= 128) ? 2 : 1;
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);
p.o_part = sc.o_part;
p.ml_part = sc.ml_part;
attn_decode_split_kv_mma_kernel<HEAD_DIM, BC, STAGES>
attn_decode_split_kv_mma_kernel<Traits, IsCausal, HasMask>
<<<dim3(p.kv_head, p.batch, p.num_splits), 32>>>(p);
attn_decode_combine_kernel<<<p.batch * p.q_head, p.head_dim>>>(p);
}
#endif
template <int HEAD_DIM, bool IsCausal, bool HasMask>
static void launch_scalar_decode(AttentionParams<bf16>& p, DecodeScratch& sc) {
int gs = p.q_head / p.kv_head;
int chunks_total = (p.kv_len + DC_CHUNK - 1) / DC_CHUNK;
@@ -48,16 +42,36 @@ static void launch_scalar_decode(AttentionParams<bf16>& p, DecodeScratch& sc) {
p.ml_part = sc.ml_part;
size_t smem = DC_CHUNK * p.head_dim * sizeof(bf16);
attn_decode_split_kv_kernel<<<dim3(p.batch * p.kv_head, 1, p.num_splits), dim3(32, gs), smem>>>(p);
attn_decode_split_kv_kernel<HEAD_DIM, IsCausal, HasMask>
<<<dim3(p.batch * p.kv_head, 1, p.num_splits), dim3(32, gs), smem>>>(p);
attn_decode_combine_kernel<<<p.batch * p.q_head, p.head_dim>>>(p);
}
template <int HEAD_DIM>
static void dispatch_decode_t(AttentionParams<bf16>& p, DecodeScratch& sc) {
bool is_causal = (p.causal_offset >= 0);
bool has_mask = (p.use_mask && p.mask);
#ifndef ASTRAI_NO_MMA
if (decode_use_mma(p)) { launch_mma_decode<HEAD_DIM, 32>(p, sc); return; }
int G = p.q_head / p.kv_head;
if (G >= 1 && G <= 16) {
if (is_causal) {
if (has_mask) launch_mma_decode<HEAD_DIM, 32, true, true>(p, sc);
else launch_mma_decode<HEAD_DIM, 32, true, false>(p, sc);
} else {
if (has_mask) launch_mma_decode<HEAD_DIM, 32, false, true>(p, sc);
else launch_mma_decode<HEAD_DIM, 32, false, false>(p, sc);
}
return;
}
#endif
launch_scalar_decode(p, sc);
if (is_causal) {
if (has_mask) launch_scalar_decode<HEAD_DIM, true, true>(p, sc);
else launch_scalar_decode<HEAD_DIM, true, false>(p, sc);
} else {
if (has_mask) launch_scalar_decode<HEAD_DIM, false, true>(p, sc);
else launch_scalar_decode<HEAD_DIM, false, false>(p, sc);
}
}
static void dispatch_decode(AttentionParams<bf16>& p, DecodeScratch& sc) {
@@ -123,77 +137,92 @@ static void bench() {
}
}
static int run_test(int B, int Hq, int Hk, int sl, int D, int causal) {
int gs = Hq / Hk;
printf("=== B=%d Hq=%d Hk=%d seq=%d D=%d gs=%d causal=%d ===\n",
B,Hq,Hk,sl,D,gs,causal);
size_t nQ = B*Hq*1*D, nKV = B*Hk*sl*D;
float *hQ=new float[nQ], *hK=new float[nKV], *hV=new float[nKV];
for (size_t i=0;i<nQ;i++) hQ[i]=randf();
for (size_t i=0;i<nKV;i++){hK[i]=randf();hV[i]=randf();}
bool* hMask=new bool[B*sl];
for (int i=0;i<B*sl;i++) hMask[i]=true;
bf16 *dQ,*dK,*dV,*dO,*tmp;
bool* dMask;
cudaMalloc(&dQ,nQ*2); cudaMalloc(&dK,nKV*2);
cudaMalloc(&dV,nKV*2); cudaMalloc(&dO,nQ*2);
cudaMalloc(&dMask,B*sl);
tmp=new bf16[max(nQ,nKV)];
for (size_t i=0;i<nQ;i++) tmp[i]=f2bf(hQ[i]);
cudaMemcpy(dQ,tmp,nQ*2,cudaMemcpyHostToDevice);
for (size_t i=0;i<nKV;i++) tmp[i]=f2bf(hK[i]);
cudaMemcpy(dK,tmp,nKV*2,cudaMemcpyHostToDevice);
for (size_t i=0;i<nKV;i++) tmp[i]=f2bf(hV[i]);
cudaMemcpy(dV,tmp,nKV*2,cudaMemcpyHostToDevice);
cudaMemcpy(dMask,hMask,B*sl,cudaMemcpyHostToDevice);
AttentionParams<bf16> p;
p.batch=B; p.q_head=Hq; p.kv_head=Hk; p.q_len=1; p.kv_len=sl; p.head_dim=D;
p.use_mask=0; p.causal_offset=causal?0:-1;
p.scale=1.0f/sqrtf((float)D);
set_default_strides(p);
p.q=dQ; p.k=dK; p.v=dV; p.mask=nullptr; p.o=dO;
DecodeScratch sc;
cudaMalloc(&sc.o_part, (size_t)B*Hq*32*D*sizeof(float));
cudaMalloc(&sc.ml_part, (size_t)B*Hq*32*2*sizeof(float));
double t0=now_ms();
dispatch_decode(p, sc);
cudaDeviceSynchronize();
double kms=now_ms()-t0;
cudaError_t err=cudaGetLastError();
if (err!=cudaSuccess){printf("CUDA err: %s\n",cudaGetErrorString(err));return 1;}
bf16* hOut=new bf16[nQ];
cudaMemcpy(hOut,dO,nQ*2,cudaMemcpyDeviceToHost);
float* ref=new float[nQ];
cpu_attention_ref(hQ, hK, hV, hMask, ref, B, Hq, Hk, 1, sl, D, causal ? 0 : -1);
float max_err=0;
for (size_t i=0;i<nQ;i++){
float d=fabsf(bf2f(hOut[i])-ref[i]);
if(d>max_err) max_err=d;
}
printf("kernel: %.3f ms max_err: %.6e\n\n",kms,max_err);
cudaFree(dQ);cudaFree(dK);cudaFree(dV);cudaFree(dO);cudaFree(dMask);
cudaFree(sc.o_part);cudaFree(sc.ml_part);
delete[]hQ;delete[]hK;delete[]hV;delete[]hMask;delete[]hOut;delete[]ref;delete[]tmp;
return (max_err < 0.05f) ? 0 : 1;
}
int main() {
const int configs[][5] = {
{1, 2, 1, 64, 32}, // B,Hq,Hk,seq_len,D
{1, 32, 4, 512, 128},
{1, 32, 4, 1024, 128},
const int configs[][6] = {
{1, 2, 1, 64, 32, 0}, // B,Hq,Hk,seq_len,D,causal
{1, 32, 4, 512, 128, 0},
{1, 32, 4, 1024, 128, 0},
{1, 32, 4, 512, 128, 1}, // causal decode
};
int n_cfgs = sizeof(configs) / sizeof(configs[0]);
int fail = 0;
for (int ci = 0; ci < n_cfgs; ci++) {
int B = configs[ci][0], Hq = configs[ci][1], Hk = configs[ci][2];
int sl = configs[ci][3], D = configs[ci][4], gs = Hq / Hk;
printf("=== B=%d Hq=%d Hk=%d seq=%d D=%d gs=%d ===\n", B,Hq,Hk,sl,D,gs);
int sl = configs[ci][3], D = configs[ci][4], causal = configs[ci][5];
fail += run_test(B, Hq, Hk, sl, D, causal);
if (fail) break;
}
size_t nQ = B*Hq*1*D, nKV = B*Hk*sl*D;
float *hQ=new float[nQ], *hK=new float[nKV], *hV=new float[nKV];
for (size_t i=0;i<nQ;i++) hQ[i]=randf();
for (size_t i=0;i<nKV;i++){hK[i]=randf();hV[i]=randf();}
bool* hMask=new bool[B*sl];
for (int i=0;i<B*sl;i++) hMask[i]=true;
bf16 *dQ,*dK,*dV,*dO,*tmp;
bool* dMask;
cudaMalloc(&dQ,nQ*2); cudaMalloc(&dK,nKV*2);
cudaMalloc(&dV,nKV*2); cudaMalloc(&dO,nQ*2);
cudaMalloc(&dMask,B*sl);
tmp=new bf16[max(nQ,nKV)];
for (size_t i=0;i<nQ;i++) tmp[i]=f2bf(hQ[i]);
cudaMemcpy(dQ,tmp,nQ*2,cudaMemcpyHostToDevice);
for (size_t i=0;i<nKV;i++) tmp[i]=f2bf(hK[i]);
cudaMemcpy(dK,tmp,nKV*2,cudaMemcpyHostToDevice);
for (size_t i=0;i<nKV;i++) tmp[i]=f2bf(hV[i]);
cudaMemcpy(dV,tmp,nKV*2,cudaMemcpyHostToDevice);
cudaMemcpy(dMask,hMask,B*sl,cudaMemcpyHostToDevice);
AttentionParams<bf16> p;
p.batch=B; p.q_head=Hq; p.kv_head=Hk; p.q_len=1; p.kv_len=sl; p.head_dim=D;
p.use_mask=0; p.causal_offset=-1;
p.scale=1.0f/sqrtf((float)D);
set_default_strides(p);
p.q=dQ; p.k=dK; p.v=dV; p.mask=nullptr; p.o=dO;
// Split-K scratch (max 32 splits), sized for the production MMA path.
DecodeScratch sc;
cudaMalloc(&sc.o_part, (size_t)B*Hq*32*D*sizeof(float));
cudaMalloc(&sc.ml_part, (size_t)B*Hq*32*2*sizeof(float));
double t0=now_ms();
dispatch_decode(p, sc);
cudaDeviceSynchronize();
double kms=now_ms()-t0;
cudaError_t err=cudaGetLastError();
if (err!=cudaSuccess){printf("CUDA err: %s\n",cudaGetErrorString(err));return 1;}
bf16* hOut=new bf16[nQ];
cudaMemcpy(hOut,dO,nQ*2,cudaMemcpyDeviceToHost);
float* ref=new float[nQ];
cpu_attention_ref(hQ, hK, hV, hMask, ref, B, Hq, Hk, 1, sl, D, -1);
float max_err=0;
for (size_t i=0;i<nQ;i++){
float d=fabsf(bf2f(hOut[i])-ref[i]);
if(d>max_err) max_err=d;
}
printf("kernel: %.3f ms max_err: %.6e\n\n",kms,max_err);
cudaFree(dQ);cudaFree(dK);cudaFree(dV);cudaFree(dO);cudaFree(dMask);
cudaFree(sc.o_part);cudaFree(sc.ml_part);
delete[]hQ;delete[]hK;delete[]hV;delete[]hMask;delete[]hOut;delete[]ref;delete[]tmp;
if (fail) {
printf("FAILED\n");
return fail;
}
printf("All tests passed!\n");
bench();