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0cc4m merged 2 commits into from
Feb 18, 2026
Merged

vulkan: split mul_mat into multiple dispatches to avoid overflow #19509

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66d7c14
vulkan: split mul_mat into multiple dispatches to avoid overflow
jeffbolznv Feb 11, 2026
feb3eef
address feedback
jeffbolznv Feb 13, 2026
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80 changes: 53 additions & 27 deletions ggml/src/ggml-vulkan/ggml-vulkan.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -942,6 +942,7 @@ struct vk_mat_mat_push_constants {
uint32_t M; uint32_t N; uint32_t K;
uint32_t stride_a; uint32_t stride_b; uint32_t stride_d;
uint32_t batch_stride_a; uint32_t batch_stride_b; uint32_t batch_stride_d;
uint32_t base_work_group_z; uint32_t num_batches;
uint32_t k_split;
uint32_t ne02; uint32_t ne12; uint32_t broadcast2; uint32_t broadcast3;
uint32_t padded_N;
Expand All @@ -961,6 +962,7 @@ struct vk_mat_vec_push_constants {
uint32_t batch_stride_b;
uint32_t batch_stride_d;
uint32_t fusion_flags;
uint32_t base_work_group_y;
uint32_t ne02;
uint32_t ne12;
uint32_t broadcast2;
Expand Down Expand Up @@ -6766,8 +6768,16 @@ static void ggml_vk_matmul(
uint32_t padded_n) {
VK_LOG_DEBUG("ggml_vk_matmul(a: (" << a.buffer->buffer << ", " << a.offset << ", " << a.size << "), b: (" << b.buffer->buffer << ", " << b.offset << ", " << b.size << "), d: (" << d.buffer->buffer << ", " << d.offset << ", " << d.size << "), split_k: (" << (split_k_buffer.buffer != nullptr ? split_k_buffer.buffer->buffer : VK_NULL_HANDLE) << ", " << split_k_buffer.offset << ", " << split_k_buffer.size << "), m: " << m << ", n: " << n << ", k: " << k << ", stride_a: " << stride_a << ", stride_b: " << stride_b << ", stride_d: " << stride_d << ", batch_stride_a: " << batch_stride_a << ", batch_stride_b: " << batch_stride_b << ", batch_stride_d: " << batch_stride_d << ", split_k: " << split_k << ", batch: " << batch << ", ne02: " << ne02 << ", ne12: " << ne12 << ", broadcast2: " << broadcast2 << ", broadcast3: " << broadcast3 << ", padded_n: " << padded_n << ")");
if (split_k == 1) {
const vk_mat_mat_push_constants pc = { m, n, k, stride_a, stride_b, stride_d, batch_stride_a, batch_stride_b, batch_stride_d, k, ne02, ne12, broadcast2, broadcast3, padded_n };
ggml_vk_dispatch_pipeline(ctx, subctx, pipeline, { a, b, d }, pc, { m, n, batch });
ggml_pipeline_request_descriptor_sets(ctx, pipeline, CEIL_DIV(batch, ctx->device->properties.limits.maxComputeWorkGroupCount[2]));

uint32_t base_work_group_z = 0;
while (base_work_group_z < batch) {
uint32_t groups_z = std::min(batch - base_work_group_z, ctx->device->properties.limits.maxComputeWorkGroupCount[2]);

const vk_mat_mat_push_constants pc = { m, n, k, stride_a, stride_b, stride_d, batch_stride_a, batch_stride_b, batch_stride_d, base_work_group_z, batch, k, ne02, ne12, broadcast2, broadcast3, padded_n };
ggml_vk_dispatch_pipeline(ctx, subctx, pipeline, { a, b, d }, pc, { m, n, groups_z });
base_work_group_z += groups_z;
}
return;
}

Expand All @@ -6781,9 +6791,17 @@ static void ggml_vk_matmul(
uint32_t k_split = CEIL_DIV(k, split_k);
k_split = ROUNDUP_POW2(k_split, 256);

const vk_mat_mat_push_constants pc1 = { m, n, k, stride_a, stride_b, stride_d, batch_stride_a, batch_stride_b, batch_stride_d, k_split, ne02, ne12, broadcast2, broadcast3, padded_n };
// Make sure enough workgroups get assigned for split k to work
ggml_vk_dispatch_pipeline(ctx, subctx, pipeline, { a, b, split_k_buffer }, pc1, { (CEIL_DIV(m, pipeline->wg_denoms[0]) * pipeline->wg_denoms[0]) * split_k, n, batch });
ggml_pipeline_request_descriptor_sets(ctx, pipeline, CEIL_DIV(batch, ctx->device->properties.limits.maxComputeWorkGroupCount[2]));

uint32_t base_work_group_z = 0;
while (base_work_group_z < batch) {
uint32_t groups_z = std::min(batch - base_work_group_z, ctx->device->properties.limits.maxComputeWorkGroupCount[2]);

const vk_mat_mat_push_constants pc1 = { m, n, k, stride_a, stride_b, stride_d, batch_stride_a, batch_stride_b, batch_stride_d, base_work_group_z, batch, k_split, ne02, ne12, broadcast2, broadcast3, padded_n };
// Make sure enough workgroups get assigned for split k to work
ggml_vk_dispatch_pipeline(ctx, subctx, pipeline, { a, b, split_k_buffer }, pc1, { (CEIL_DIV(m, pipeline->wg_denoms[0]) * pipeline->wg_denoms[0]) * split_k, n, groups_z });
base_work_group_z += groups_z;
}
ggml_vk_sync_buffers(ctx, subctx);
const std::array<uint32_t, 2> pc2 = { (uint32_t)(m * n * batch), split_k };
ggml_vk_dispatch_pipeline(ctx, subctx, ctx->device->pipeline_matmul_split_k_reduce, { split_k_buffer, d }, pc2, { m * n * batch, 1, 1 });
Expand Down Expand Up @@ -7179,7 +7197,6 @@ static void ggml_vk_mul_mat_q_f16(ggml_backend_vk_context * ctx, vk_context& sub
}

// Request descriptor sets
ggml_pipeline_request_descriptor_sets(ctx, pipeline, 1);
if (qx_needs_dequant) {
ggml_pipeline_request_descriptor_sets(ctx, to_fp16_vk_0, 1);
}
Expand Down Expand Up @@ -7477,7 +7494,6 @@ static void ggml_vk_mul_mat_vec_q_f16(ggml_backend_vk_context * ctx, vk_context&
if (quantize_y) {
ggml_pipeline_request_descriptor_sets(ctx, to_q8_1, 1);
}
ggml_pipeline_request_descriptor_sets(ctx, dmmv, 1);
}

vk_subbuffer d_D = ggml_vk_tensor_subbuffer(ctx, cgraph->nodes[node_idx + ctx->num_additional_fused_ops]);
Expand Down Expand Up @@ -7572,22 +7588,29 @@ static void ggml_vk_mul_mat_vec_q_f16(ggml_backend_vk_context * ctx, vk_context&
fusion_flags |= MAT_VEC_FUSION_FLAGS_BIAS1;
}

// compute
const vk_mat_vec_push_constants pc = {
(uint32_t)ne00, (uint32_t)ne10, (uint32_t)ne10, (uint32_t)ne01,
stride_batch_x, stride_batch_y, stride_batch_d,
fusion_flags,
(uint32_t)ne02, (uint32_t)ne12, (uint32_t)r2, (uint32_t)r3,
};
ggml_vk_dispatch_pipeline(ctx, subctx, dmmv,
{
d_X,
d_Y,
d_D,
d_F0,
d_F1,
},
pc, { groups_x, (uint32_t)(ne12 * ne13), groups_z });
ggml_pipeline_request_descriptor_sets(ctx, dmmv, CEIL_DIV(ne12 * ne13, ctx->device->properties.limits.maxComputeWorkGroupCount[1]));

uint32_t base_work_group_y = 0;
while (base_work_group_y < ne12 * ne13) {

uint32_t groups_y = std::min((uint32_t)(ne12 * ne13) - base_work_group_y, ctx->device->properties.limits.maxComputeWorkGroupCount[1]);
const vk_mat_vec_push_constants pc = {
(uint32_t)ne00, (uint32_t)ne10, (uint32_t)ne10, (uint32_t)ne01,
stride_batch_x, stride_batch_y, stride_batch_d,
fusion_flags, base_work_group_y,
(uint32_t)ne02, (uint32_t)ne12, (uint32_t)r2, (uint32_t)r3,
};
ggml_vk_dispatch_pipeline(ctx, subctx, dmmv,
{
d_X,
d_Y,
d_D,
d_F0,
d_F1,
},
pc, { groups_x, groups_y, groups_z });
base_work_group_y += groups_y;
}

if (x_non_contig) {
ctx->prealloc_x_need_sync = true;
Expand Down Expand Up @@ -7825,10 +7848,15 @@ static void ggml_vk_mul_mat(ggml_backend_vk_context * ctx, vk_context& subctx, c
src1->nb[2] <= src1->nb[1] &&
src1->nb[1] <= src1->nb[3] &&
src0->ne[3] == 1 &&
src1->ne[3] == 1) {
src1->ne[3] == 1 &&
src0->ne[1] <= ctx->device->properties.limits.maxComputeWorkGroupCount[1] &&
src1->ne[2] <= ctx->device->properties.limits.maxComputeWorkGroupCount[2]) {
ggml_vk_mul_mat_vec_p021_f16_f32(ctx, subctx, cgraph, node_idx);
} else if (src0->type == GGML_TYPE_F16 && !ggml_is_contiguous(src0) && !ggml_is_transposed(src1) && dst->ne[1] == 1 &&
!ggml_is_permuted(src0) && !ggml_is_permuted(src1)) {
!ggml_is_permuted(src0) && !ggml_is_permuted(src1) &&
src0->ne[3] <= ctx->device->properties.limits.maxComputeWorkGroupCount[0] &&
src0->ne[1] <= ctx->device->properties.limits.maxComputeWorkGroupCount[1] &&
src1->ne[2] <= ctx->device->properties.limits.maxComputeWorkGroupCount[2]) {
ggml_vk_mul_mat_vec_nc_f16_f32(ctx, subctx, cgraph, node_idx);
// mul_mat_vec supports batching ne12*ne13 when ne11==1, or treating ne11 as the batch size (up to four)
// when ne12 and ne13 are one.
Expand Down Expand Up @@ -11543,7 +11571,6 @@ static void ggml_vk_test_matmul(ggml_backend_vk_context * ctx, size_t m, size_t
}
}

ggml_pipeline_request_descriptor_sets(ctx, p, num_it);
if (split_k > 1) {
ggml_pipeline_request_descriptor_sets(ctx, ctx->device->pipeline_matmul_split_k_reduce, num_it);

Expand Down Expand Up @@ -12052,7 +12079,6 @@ static void ggml_vk_test_dequant_matmul(ggml_backend_vk_context * ctx, size_t m,
// y[i] = i % k;
}

ggml_pipeline_request_descriptor_sets(ctx, p, num_it);
if (split_k > 1) {
ggml_pipeline_request_descriptor_sets(ctx, ctx->device->pipeline_matmul_split_k_reduce, num_it);

Expand Down
5 changes: 3 additions & 2 deletions ggml/src/ggml-vulkan/vulkan-shaders/mul_mat_vec_base.glsl
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@ layout (push_constant) uniform parameter
uint expert_i1;
uint nbi1;
#else
uint base_work_group_y;
uint ne02;
uint ne12;
uint broadcast2;
Expand All @@ -45,9 +46,9 @@ uint expert_id;

void get_offsets(out uint a_offset, out uint b_offset, out uint d_offset) {
#ifdef MUL_MAT_ID
const uint expert_i0 = gl_GlobalInvocationID.y;
const uint expert_i0 = gl_WorkGroupID.y;
#else
const uint batch_idx = gl_GlobalInvocationID.y;
const uint batch_idx = gl_WorkGroupID.y + p.base_work_group_y;
#endif

#ifndef MUL_MAT_ID
Expand Down
8 changes: 5 additions & 3 deletions ggml/src/ggml-vulkan/vulkan-shaders/mul_mm.comp
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Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,8 @@ layout (push_constant) uniform parameter
uint nbi1;
uint ne11;
#else
uint base_work_group_z;
uint num_batches;
uint k_split;
uint ne02;
uint ne12;
Expand Down Expand Up @@ -139,7 +141,7 @@ void main() {
const uint ic = gl_WorkGroupID.y;

#ifdef MUL_MAT_ID
const uint expert_idx = gl_GlobalInvocationID.z;
const uint expert_idx = gl_WorkGroupID.z;
if (ic * BN >= data_expert_count[expert_idx]) {
return;
}
Expand All @@ -149,7 +151,7 @@ void main() {
#endif

#ifndef MUL_MAT_ID
const uint batch_idx = gl_GlobalInvocationID.z;
const uint batch_idx = gl_WorkGroupID.z + p.base_work_group_z;

const uint i13 = batch_idx / p.ne12;
const uint i12 = batch_idx % p.ne12;
Expand Down Expand Up @@ -366,7 +368,7 @@ void main() {
const uint dc = ic * BN + warp_c * WN;

#ifndef MUL_MAT_ID
const uint offsets = batch_idx * p.batch_stride_d + ik * p.batch_stride_d * gl_NumWorkGroups.z;
const uint offsets = batch_idx * p.batch_stride_d + ik * p.batch_stride_d * p.num_batches;
#endif

#ifdef COOPMAT
Expand Down
8 changes: 5 additions & 3 deletions ggml/src/ggml-vulkan/vulkan-shaders/mul_mm_cm2.comp
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,8 @@ layout (push_constant) uniform parameter
uint nbi1;
uint ne11;
#else
uint base_work_group_z;
uint num_batches;
uint k_split;
uint ne02;
uint ne12;
Expand Down Expand Up @@ -197,7 +199,7 @@ void main() {
const uint ic = gl_WorkGroupID.y;

#ifdef MUL_MAT_ID
const uint expert_idx = gl_GlobalInvocationID.z;
const uint expert_idx = gl_WorkGroupID.z;
if (ic * BN >= data_expert_count[expert_idx]) {
return;
}
Expand All @@ -215,7 +217,7 @@ void main() {
#endif

#ifndef MUL_MAT_ID
const uint batch_idx = gl_GlobalInvocationID.z;
const uint batch_idx = gl_WorkGroupID.z + p.base_work_group_z;

const uint i13 = batch_idx / p.ne12;
const uint i12 = batch_idx % p.ne12;
Expand Down Expand Up @@ -255,7 +257,7 @@ void main() {
#else
uint pos_a = batch_idx_a * (p.batch_stride_a / QUANT_K);
uint pos_b = batch_idx * p.batch_stride_b;
uint pos_d = batch_idx * p.batch_stride_d + ik * p.batch_stride_d * gl_NumWorkGroups.z;
uint pos_d = batch_idx * p.batch_stride_d + ik * p.batch_stride_d * p.num_batches;
#endif

uint stride_a = p.stride_a / QUANT_K;
Expand Down
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