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[Bugfix][Kernel] silu_and_mul_quant: run the vectorized loop #61716

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Merged
khluu merged 2 commits into from
Oct 16, 2026
Merged

[Bugfix][Kernel] silu_and_mul_quant: run the vectorized loop #61716

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7efbba1
[Bugfix][Kernel] silu_and_mul_quant: run the vectorized loop
Monishver11 Oct 14, 2026
7db867f
Merge branch 'main' into fix/silu-mul-quant-vector-loop
khluu Oct 15, 2026
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56 changes: 32 additions & 24 deletions csrc/quantization/activation_kernels.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@

#include "core/utils.hpp"
#include "core/cuda_compat.h"
#include "cuda_vec_utils.cuh"
#include "dispatch_utils.h"
#include "quantization/w8a8/fp8/common.cuh"

Expand Down Expand Up @@ -43,7 +44,7 @@ template <typename scalar_t, scalar_t (*ACT_FN)(const scalar_t&),
__global__ void act_and_mul_quant_kernel(
fp8_type* __restrict__ out, // [..., d]
const scalar_t* __restrict__ input, // [..., 2, d]
const float* scale, const int d) {
const float* scale, const int d, const bool vectorize) {
const int32_t blocks_per_token = gridDim.y;

const int32_t elems_per_128bit_load = (128 / 8) / sizeof(scalar_t);
Expand All @@ -64,9 +65,12 @@ __global__ void act_and_mul_quant_kernel(
const scalar_t* __restrict__ y_ptr = input + token_idx * 2 * d + d;
fp8_type* __restrict__ out_ptr = out + token_idx * d;

// 128-bit vectorized code
const int32_t vec_loop_end =
round_to_previous_multiple_of(elems_per_128bit_load, block_end);
// 128-bit vectorized code, when d and the data pointers allow 16-byte
// loads and 8-byte stores on every row; otherwise the cleanup loop below
// handles the whole block.
const int32_t vec_loop_end = vectorize ? round_to_previous_multiple_of(
block_end, elems_per_128bit_load)
: block_start;
const int32_t vec_end_idx = vec_loop_end / elems_per_128bit_load;
const int32_t vec_start_idx = block_start / elems_per_128bit_load;

Expand Down Expand Up @@ -559,26 +563,30 @@ __global__ void silu_mul_fp8_quant_deep_gemm_kernel(
} // namespace vllm

// Launch activation, gating, and quantize kernel.
#define LAUNCH_ACTIVATION_GATE_KERNEL(KERNEL) \
int d = input.size(-1) / 2; \
int64_t num_tokens = input.numel() / input.size(-1); \
dim3 grid(num_tokens, num_tokens > 16 ? num_tokens > 32 ? 1 : 2 : 4); \
dim3 block(std::min(d, 512)); \
const torch::stable::accelerator::DeviceGuard device_guard( \
input.get_device_index()); \
const cudaStream_t stream = \
get_current_cuda_stream(input.get_device_index()); \
VLLM_STABLE_DISPATCH_FLOATING_TYPES( \
input.scalar_type(), "act_and_mul_kernel", [&] { \
VLLM_STABLE_DISPATCH_FP8_TYPES( \
out.scalar_type(), "act_and_mul_quant_kernel_fp8_type", [&] { \
vllm::act_and_mul_quant_kernel<scalar_t, KERNEL<scalar_t>, \
fp8_t> \
<<<grid, block, 0, stream>>>( \
out.mutable_data_ptr<fp8_t>(), \
input.const_data_ptr<scalar_t>(), \
scale.const_data_ptr<float>(), d); \
}); \
#define LAUNCH_ACTIVATION_GATE_KERNEL(KERNEL) \
int d = input.size(-1) / 2; \
int64_t num_tokens = input.numel() / input.size(-1); \
dim3 grid(num_tokens, num_tokens > 16 ? num_tokens > 32 ? 1 : 2 : 4); \
dim3 block(std::min(d, 512)); \
const torch::stable::accelerator::DeviceGuard device_guard( \
input.get_device_index()); \
const cudaStream_t stream = \
get_current_cuda_stream(input.get_device_index()); \
VLLM_STABLE_DISPATCH_FLOATING_TYPES( \
input.scalar_type(), "act_and_mul_kernel", [&] { \
VLLM_STABLE_DISPATCH_FP8_TYPES( \
out.scalar_type(), "act_and_mul_quant_kernel_fp8_type", [&] { \
const scalar_t* in_ptr = input.const_data_ptr<scalar_t>(); \
fp8_t* out_ptr = out.mutable_data_ptr<fp8_t>(); \
const bool vectorize = d % (16 / sizeof(scalar_t)) == 0 && \
vllm::is_16byte_aligned(in_ptr) && \
vllm::is_16byte_aligned(out_ptr); \
vllm::act_and_mul_quant_kernel<scalar_t, KERNEL<scalar_t>, \
fp8_t> \
<<<grid, block, 0, stream>>>(out_ptr, in_ptr, \
scale.const_data_ptr<float>(), \
d, vectorize); \
}); \
});

void silu_and_mul_quant(torch::stable::Tensor& out, // [..., d]
Expand Down
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