vulkan: fix coopmat2 flash attention for non-contiguous inputs (ggml-org#11281)

jeffbolznv · NeoZhangJianyu · commit 03b025b321c6 · 2025-02-25T17:49:53.000+08:00
Add code similar to mul_mm_cm2 to force alignment of strides, to avoid a performance regression. Add noncontiguous FA tests in test-backend-ops. Fixes ggml-org#11268.
diff --git a/ggml/src/ggml-vulkan/ggml-vulkan.cpp b/ggml/src/ggml-vulkan/ggml-vulkan.cpp
@@ -386,10 +386,13 @@ struct vk_flash_attn_push_constants {
     uint32_t nev3;
     uint32_t nem1;
 
+    uint32_t nb01;
     uint32_t nb02;
     uint32_t nb03;
+    uint32_t nb11;
     uint32_t nb12;
     uint32_t nb13;
+    uint32_t nb21;
     uint32_t nb22;
     uint32_t nb23;
     uint32_t nb31;
@@ -4809,7 +4812,14 @@ static void ggml_vk_flash_attn(ggml_backend_vk_context * ctx, vk_context& subctx
     }
     assert(pipelines);
 
-    bool aligned = (KV % pipelines[1]->align) == 0;
+    const uint32_t q_stride = (uint32_t)(nbq1 / ggml_type_size(q->type));
+    const uint32_t k_stride = (uint32_t)(nbk1 / ggml_type_size(k->type));
+    const uint32_t v_stride = (uint32_t)(nbv1 / ggml_type_size(v->type));
+
+    bool aligned = (KV % pipelines[1]->align) == 0 &&
+                   // the "aligned" shader variant will forcibly align strides, for performance
+                   (q_stride & 7) == 0 && (k_stride & 7) == 0 && (v_stride & 7) == 0;
+
     vk_pipeline pipeline = pipelines[aligned];
     assert(pipeline);
 
@@ -4845,15 +4855,15 @@ static void ggml_vk_flash_attn(ggml_backend_vk_context * ctx, vk_context& subctx
 
     if (ctx->device->uma) {
         ggml_vk_host_get(ctx->device, q->data, d_Q, q_buf_offset);
-        ggml_vk_host_get(ctx->device, k->data, d_K, q_buf_offset);
-        ggml_vk_host_get(ctx->device, v->data, d_V, q_buf_offset);
-        ggml_vk_host_get(ctx->device, dst->data, d_D, q_buf_offset);
+        ggml_vk_host_get(ctx->device, k->data, d_K, k_buf_offset);
+        ggml_vk_host_get(ctx->device, v->data, d_V, v_buf_offset);
+        ggml_vk_host_get(ctx->device, dst->data, d_D, d_buf_offset);
         Q_uma = d_Q != nullptr;
         K_uma = d_K != nullptr;
         V_uma = d_V != nullptr;
         D_uma = d_D != nullptr;
         if (mask) {
-            ggml_vk_host_get(ctx->device, mask->data, d_M, q_buf_offset);
+            ggml_vk_host_get(ctx->device, mask->data, d_M, m_buf_offset);
             M_uma = d_M != nullptr;
         }
     }
@@ -4891,7 +4901,18 @@ static void ggml_vk_flash_attn(ggml_backend_vk_context * ctx, vk_context& subctx
         }
     }
 
-    const vk_flash_attn_push_constants pc = { N, KV, (uint32_t)ne1, (uint32_t)ne2, (uint32_t)ne3, (uint32_t)neq2, (uint32_t)neq3, (uint32_t)nek2, (uint32_t)nek3, (uint32_t)nev2, (uint32_t)nev3, nem1, (uint32_t)nbq2, (uint32_t)nbq3, (uint32_t)nbk2, (uint32_t)nbk3, (uint32_t)nbv2, (uint32_t)nbv3, nbm1, scale, max_bias, logit_softcap, mask != nullptr, n_head_log2, m0, m1 };
+    const vk_flash_attn_push_constants pc = { N, KV,
+                                              (uint32_t)ne1, (uint32_t)ne2, (uint32_t)ne3,
+                                              (uint32_t)neq2, (uint32_t)neq3,
+                                              (uint32_t)nek2, (uint32_t)nek3,
+                                              (uint32_t)nev2, (uint32_t)nev3,
+                                              nem1,
+                                              q_stride, (uint32_t)nbq2, (uint32_t)nbq3,
+                                              k_stride, (uint32_t)nbk2, (uint32_t)nbk3,
+                                              v_stride, (uint32_t)nbv2, (uint32_t)nbv3,
+                                              nbm1,
+                                              scale, max_bias, logit_softcap,
+                                              mask != nullptr, n_head_log2, m0, m1 };
     ggml_vk_dispatch_pipeline(ctx, subctx, pipeline,
                                 {
                                     vk_subbuffer{d_Q, q_buf_offset, VK_WHOLE_SIZE},
@@ -8668,6 +8689,7 @@ static void ggml_vk_check_results_1(ggml_tensor * tensor) {
     ggml_tensor * src0 = tensor->src[0];
     ggml_tensor * src1 = tensor->src[1];
     ggml_tensor * src2 = tensor->src[2];
+    ggml_tensor * src3 = tensor->src[3];
 
     void * tensor_data = tensor->data;
 
@@ -8730,6 +8752,9 @@ static void ggml_vk_check_results_1(ggml_tensor * tensor) {
                         if (src2 != nullptr) {
                             std::cerr << "src2=" << src2 << " src2->name=" << src2->name << " op=" << ggml_op_name(src2->op) << " type=" << ggml_type_name(src2->type) << " ne0=" << src2->ne[0] << " nb0=" << src2->nb[0] << " ne1=" << src2->ne[1] << " nb1=" << src2->nb[1] << " ne2=" << src2->ne[2] << " nb2=" << src2->nb[2] << " ne3=" << src2->ne[3] << " nb3=" << src2->nb[3] << " offset=" << src2->view_offs << std::endl;
                         }
+                        if (src3 != nullptr) {
+                            std::cerr << "src3=" << src3 << " src3->name=" << src3->name << " op=" << ggml_op_name(src3->op) << " type=" << ggml_type_name(src3->type) << " ne0=" << src3->ne[0] << " nb0=" << src3->nb[0] << " ne1=" << src3->ne[1] << " nb1=" << src3->nb[1] << " ne2=" << src3->ne[2] << " nb2=" << src3->nb[2] << " ne3=" << src3->ne[3] << " nb3=" << src3->nb[3] << " offset=" << src3->view_offs << std::endl;
+                        }
                         std::cerr << "First error: result=" << first_error_result << " correct=" << first_error_correct  << " i3=" << first_error[3] << " i2=" << first_error[2] << " i1=" << first_error[1] << " i0=" << first_error[0] << std::endl;
                         std::cerr << std::endl << "Result:" << std::endl;
                         ggml_vk_print_tensor_area(tensor, tensor_data, i0, i1, i2, i3);
@@ -8774,6 +8799,9 @@ static void ggml_vk_check_results_1(ggml_tensor * tensor) {
         if (src2 != nullptr) {
             std::cerr << "src2=" << src2 << " op=" << ggml_op_name(src2->op) << " type=" << ggml_type_name(src2->type) << " ne0=" << src2->ne[0] << " nb0=" << src2->nb[0] << " ne1=" << src2->ne[1] << " nb1=" << src2->nb[1] << " ne2=" << src2->ne[2] << " nb2=" << src2->nb[2] << " ne3=" << src2->ne[3] << " nb3=" << src2->nb[3] << " offset=" << src2->view_offs << std::endl;
         }
+        if (src3 != nullptr) {
+            std::cerr << "src3=" << src3 << " op=" << ggml_op_name(src3->op) << " type=" << ggml_type_name(src3->type) << " ne0=" << src3->ne[0] << " nb0=" << src3->nb[0] << " ne1=" << src3->ne[1] << " nb1=" << src3->nb[1] << " ne2=" << src3->ne[2] << " nb2=" << src3->nb[2] << " ne3=" << src3->ne[3] << " nb3=" << src3->nb[3] << " offset=" << src3->view_offs << std::endl;
+        }
         std::cerr << "First error: result=" << first_error_result << " correct=" << first_error_correct  << " i3=" << first_error[3] << " i2=" << first_error[2] << " i1=" << first_error[1] << " i0=" << first_error[0] << std::endl;
         std::cerr << std::endl << "Result:" << std::endl;
         ggml_vk_print_tensor_area(tensor, tensor_data, 5, 5, 0, 0);
@@ -8796,6 +8824,9 @@ static void ggml_vk_check_results_1(ggml_tensor * tensor) {
         if (src2 != nullptr) {
             std::cerr << "src2=" << src2 << " op=" << ggml_op_name(src2->op) << " type=" << ggml_type_name(src2->type) << " ne0=" << src2->ne[0] << " nb0=" << src2->nb[0] << " ne1=" << src2->ne[1] << " nb1=" << src2->nb[1] << " ne2=" << src2->ne[2] << " nb2=" << src2->nb[2] << " ne3=" << src2->ne[3] << " nb3=" << src2->nb[3] << " offset=" << src2->view_offs << std::endl;
         }
+        if (src3 != nullptr) {
+            std::cerr << "src3=" << src3 << " op=" << ggml_op_name(src3->op) << " type=" << ggml_type_name(src3->type) << " ne0=" << src3->ne[0] << " nb0=" << src3->nb[0] << " ne1=" << src3->ne[1] << " nb1=" << src3->nb[1] << " ne2=" << src3->ne[2] << " nb2=" << src3->nb[2] << " ne3=" << src3->ne[3] << " nb3=" << src3->nb[3] << " offset=" << src3->view_offs << std::endl;
+        }
         std::cerr << "First error: result=" << first_error_result << " correct=" << first_error_correct  << " i3=" << first_error[3] << " i2=" << first_error[2] << " i1=" << first_error[1] << " i0=" << first_error[0] << std::endl;
         std::cerr << std::endl << "Result:" << std::endl;
         ggml_vk_print_tensor_area(tensor, tensor_data, first_error[0], first_error[1], first_error[2], first_error[3]);
diff --git a/ggml/src/ggml-vulkan/vulkan-shaders/flash_attn_cm2.comp b/ggml/src/ggml-vulkan/vulkan-shaders/flash_attn_cm2.comp
@@ -42,10 +42,13 @@ layout (push_constant) uniform parameter {
     uint32_t nev3;
     uint32_t nem1;
 
+    uint32_t nb01;
     uint32_t nb02;
     uint32_t nb03;
+    uint32_t nb11;
     uint32_t nb12;
     uint32_t nb13;
+    uint32_t nb21;
     uint32_t nb22;
     uint32_t nb23;
     uint32_t nb31;
@@ -146,6 +149,23 @@ void main() {
     tensorLayoutK = setTensorLayoutDimensionNV(tensorLayoutK, KV, D);
     tensorLayoutV = setTensorLayoutDimensionNV(tensorLayoutV, KV, D);
 
+    // nb?1 are already divided by the type size and are in units of elements
+    uint32_t q_stride = p.nb01;
+    uint32_t k_stride = p.nb11;
+    uint32_t v_stride = p.nb21;
+    // hint to the compiler that strides are aligned for the aligned variant of the shader
+    if (Clamp != gl_CooperativeMatrixClampModeConstantNV)
+    {
+        q_stride &= ~7;
+#if !defined(BLOCK_SIZE)
+        k_stride &= ~7;
+        v_stride &= ~7;
+#endif
+    }
+    tensorLayoutQ = setTensorLayoutStrideNV(tensorLayoutQ, q_stride, 1);
+    tensorLayoutK = setTensorLayoutStrideNV(tensorLayoutK, k_stride, 1);
+    tensorLayoutV = setTensorLayoutStrideNV(tensorLayoutV, v_stride, 1);
+
     coopmat<Q_TYPE, gl_ScopeWorkgroup, Br, D, gl_MatrixUseA> Q;
     coopmat<float16_t, gl_ScopeWorkgroup, Br, D, gl_MatrixUseA> Qf16;
 
diff --git a/tests/test-backend-ops.cpp b/tests/test-backend-ops.cpp
@@ -3046,9 +3046,10 @@ struct test_flash_attn_ext : public test_case {
     const float logit_softcap; // Gemma 2
 
     const ggml_type type_KV;
+    std::array<int32_t, 4> permute;
 
     std::string vars() override {
-        return VARS_TO_STR8(hs, nh, kv, nb, mask, max_bias, logit_softcap, type_KV);
+        return VARS_TO_STR9(hs, nh, kv, nb, mask, max_bias, logit_softcap, type_KV, permute);
     }
 
     double max_nmse_err() override {
@@ -3063,19 +3064,33 @@ struct test_flash_attn_ext : public test_case {
     }
 
     test_flash_attn_ext(int64_t hs = 128, int64_t nh = 32, int64_t kv = 96, int64_t nb = 8,
-                        bool mask = true, float max_bias = 0.0f, float logit_softcap = 0.0f, ggml_type type_KV = GGML_TYPE_F16)
-        : hs(hs), nh(nh), kv(kv), nb(nb), mask(mask), max_bias(max_bias), logit_softcap(logit_softcap), type_KV(type_KV) {}
+                        bool mask = true, float max_bias = 0.0f, float logit_softcap = 0.0f, ggml_type type_KV = GGML_TYPE_F16,
+                        std::array<int32_t, 4> permute = {0, 1, 2, 3})
+        : hs(hs), nh(nh), kv(kv), nb(nb), mask(mask), max_bias(max_bias), logit_softcap(logit_softcap), type_KV(type_KV), permute(permute) {}
 
     ggml_tensor * build_graph(ggml_context * ctx) override {
         const int64_t hs_padded = GGML_PAD(hs, ggml_blck_size(type_KV));
 
-        ggml_tensor * q = ggml_new_tensor_4d(ctx, GGML_TYPE_F32, hs_padded, nb, nh, 1);
+        auto const &create_permuted = [&](ggml_type type, int64_t ne0, int64_t ne1, int64_t ne2, int64_t ne3) -> ggml_tensor * {
+            int64_t ne[4] = {ne0, ne1, ne2, ne3};
+            int64_t ne_perm[4];
+            for (int i = 0; i < 4; ++i) {
+                ne_perm[permute[i]] = ne[i];
+            }
+            ggml_tensor * t = ggml_new_tensor_4d(ctx, type, ne_perm[0], ne_perm[1], ne_perm[2], ne_perm[3]);
+            if (permute != std::array<int32_t, 4>{0, 1, 2, 3}) {
+                t = ggml_permute(ctx, t, permute[0], permute[1], permute[2], permute[3]);
+            }
+            return t;
+        };
+
+        ggml_tensor * q = create_permuted(GGML_TYPE_F32, hs_padded, nb, nh, 1);
         ggml_set_name(q, "q");
 
-        ggml_tensor * k = ggml_new_tensor_4d(ctx, type_KV,       hs_padded, kv, nh, 1);
+        ggml_tensor * k = create_permuted(type_KV,       hs_padded, kv, nh, 1);
         ggml_set_name(k, "k");
 
-        ggml_tensor * v = ggml_new_tensor_4d(ctx, type_KV,       hs_padded, kv, nh, 1);
+        ggml_tensor * v = create_permuted(type_KV,       hs_padded, kv, nh, 1);
         ggml_set_name(v, "v");
 
         ggml_tensor * m = nullptr;
@@ -4167,6 +4182,10 @@ static std::vector<std::unique_ptr<test_case>> make_test_cases_eval() {
                             for (int nb : { 1, 3, 32, 35, }) {
                                 for (ggml_type type_KV : {GGML_TYPE_F16, GGML_TYPE_BF16, GGML_TYPE_Q8_0, GGML_TYPE_Q4_0}) {
                                     test_cases.emplace_back(new test_flash_attn_ext(hs, nh, kv, nb, mask, max_bias, logit_softcap, type_KV));
+                                    // run fewer test cases permuted
+                                    if (mask == true && max_bias == 0.0f && logit_softcap == 0 && kv == 512) {
+                                        test_cases.emplace_back(new test_flash_attn_ext(hs, nh, kv, nb, mask, max_bias, logit_softcap, type_KV, {0, 2, 1, 3}));
+                                    }
                                 }
                             }
                         }
