metal: SSM kernel improvements (llama/17876)

* feat: Add a batched version of ssm_conv

This was done using Claude Code. It found a number of optimizations around
how the threads were organized, resulting in a huge performance boost!

Branch: Mamba2SSD

Signed-off-by: Gabe Goodhart <ghart@us.ibm.com>

* feat: Optimized SSM_SCAN kernel for metal

This used Claude Code and resulted in a modest performance improvement
while maintaining correctness.

Branch: Mamba2SSD

Signed-off-by: Gabe Goodhart <ghart@us.ibm.com>

* test: Add test-backend-ops perf tests for SSM_CONV

Branch: SSMKernelImprovements

Signed-off-by: Gabe Goodhart <ghart@us.ibm.com>

* test: Real representitive tests for SSM_CONV

Branch: SSMKernelImprovements

Signed-off-by: Gabe Goodhart <ghart@us.ibm.com>

* refactor: Use function constant for ssm_conv batch size

Branch: SSMKernelImprovements

Signed-off-by: Gabe Goodhart <ghart@us.ibm.com>

* test: backend op tests for ssm_scan from granite4 1b-h

Branch: SSMKernelImprovements

Signed-off-by: Gabe Goodhart <ghart@us.ibm.com>

* style: remove commented out templates

Branch: SSMKernelImprovements

Signed-off-by: Gabe Goodhart <ghart@us.ibm.com>

* feat: float4 version of ssm_conv_batched

Branch: SSMKernelImprovements

Signed-off-by: Gabe Goodhart <ghart@us.ibm.com>

* fix: Add missing ggml_metal_cv_free

Signed-off-by: Gabe Goodhart <ghart@us.ibm.com>

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

---------

Signed-off-by: Gabe Goodhart <ghart@us.ibm.com>
Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
This commit is contained in:
Gabe Goodhart 2025-12-09 12:30:02 -07:00 committed by Georgi Gerganov
parent 2817582be2
commit 307dc525bb
No known key found for this signature in database
GPG Key ID: 449E073F9DC10735
5 changed files with 202 additions and 17 deletions

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@ -411,6 +411,38 @@ ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_ssm_conv(ggml_me
return res;
}
ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_ssm_conv_batched(ggml_metal_library_t lib, const ggml_tensor * op, int ssm_conv_bs) {
GGML_ASSERT(op->src[0]->type == GGML_TYPE_F32);
GGML_ASSERT(op->src[1]->type == GGML_TYPE_F32);
GGML_ASSERT(ggml_is_contiguous(op->src[0]));
GGML_ASSERT(ggml_is_contiguous(op->src[1]));
char base[256];
char name[256];
const char * suffix = "";
if (op->src[1]->ne[0] % 4 == 0) {
suffix = "_4";
}
snprintf(base, 256, "kernel_ssm_conv_%s_%s_batched%s", ggml_type_name(op->src[0]->type), ggml_type_name(op->src[1]->type), suffix);
snprintf(name, 256, "%s_ssm_conv_bs=%d", base, ssm_conv_bs);
ggml_metal_pipeline_with_params res = ggml_metal_library_get_pipeline(lib, name);
if (!res.pipeline) {
ggml_metal_cv_t cv = ggml_metal_cv_init();
ggml_metal_cv_set_int16(cv, ssm_conv_bs, FC_SSM_CONV + 0);
res = ggml_metal_library_compile_pipeline(lib, base, name, cv);
ggml_metal_cv_free(cv);
}
return res;
}
ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_ssm_scan(ggml_metal_library_t lib, const ggml_tensor * op) {
GGML_TENSOR_LOCALS( int32_t, ne0, op->src[0], ne);
@ -427,7 +459,12 @@ ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_ssm_scan(ggml_me
res = ggml_metal_library_compile_pipeline(lib, base, name, nullptr);
}
res.smem = 32*sizeof(float)*nsg;
// Shared memory layout:
// - sgptg * NW floats for partial sums (nsg * 32)
// - sgptg floats for shared_x_dt (nsg)
// - sgptg floats for shared_dA (nsg)
// Total: nsg * (32 + 2) floats
res.smem = (32 + 2)*sizeof(float)*nsg;
return res;
}

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@ -117,6 +117,7 @@ struct ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_cumsum_ad
struct ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_tri (ggml_metal_library_t lib, const struct ggml_tensor * op);
struct ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_soft_max (ggml_metal_library_t lib, const struct ggml_tensor * op);
struct ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_ssm_conv (ggml_metal_library_t lib, const struct ggml_tensor * op);
struct ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_ssm_conv_batched (ggml_metal_library_t lib, const struct ggml_tensor * op, int ssm_conv_bs);
struct ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_ssm_scan (ggml_metal_library_t lib, const struct ggml_tensor * op);
struct ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_rwkv (ggml_metal_library_t lib, const struct ggml_tensor * op);
struct ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_mul_mv_ext (ggml_metal_library_t lib, enum ggml_type tsrc0, enum ggml_type tsrc1, int nsg, int nxpsg, int r1ptg);

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@ -77,6 +77,7 @@
#define FC_MUL_MV 600
#define FC_MUL_MM 700
#define FC_ROPE 800
#define FC_SSM_CONV 900
// op-specific constants
#define OP_FLASH_ATTN_EXT_NQPTG 8

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@ -1365,15 +1365,43 @@ int ggml_metal_op_ssm_conv(ggml_metal_op_t ctx, int idx) {
/*.nb2 =*/ nb2,
};
auto pipeline = ggml_metal_library_get_pipeline_ssm_conv(lib, op);
// Use batched kernel for prefill (ne1 > 1) to reduce threadgroup dispatch overhead
const bool use_batched = (ne1 > 1);
ggml_metal_encoder_set_pipeline(enc, pipeline);
ggml_metal_encoder_set_bytes(enc, &args, sizeof(args), 0);
ggml_metal_encoder_set_buffer(enc, ggml_metal_get_buffer_id(op->src[0]), 1);
ggml_metal_encoder_set_buffer(enc, ggml_metal_get_buffer_id(op->src[1]), 2);
ggml_metal_encoder_set_buffer(enc, ggml_metal_get_buffer_id(op), 3);
if (use_batched) {
// Determine the smallest power of 2 that's >= ne1, but <= 256
int BATCH_SIZE;
if (ne1 > 128) BATCH_SIZE = 256;
else if (ne1 > 64 ) BATCH_SIZE = 128;
else if (ne1 > 32 ) BATCH_SIZE = 64;
else if (ne1 > 16 ) BATCH_SIZE = 32;
else if (ne1 > 8 ) BATCH_SIZE = 16;
else if (ne1 > 4 ) BATCH_SIZE = 8;
else BATCH_SIZE = 2;
ggml_metal_encoder_dispatch_threadgroups(enc, ne01, ne1, ne02, 1, 1, 1);
auto pipeline = ggml_metal_library_get_pipeline_ssm_conv_batched(lib, op, BATCH_SIZE);
ggml_metal_encoder_set_pipeline(enc, pipeline);
ggml_metal_encoder_set_bytes(enc, &args, sizeof(args), 0);
ggml_metal_encoder_set_buffer(enc, ggml_metal_get_buffer_id(op->src[0]), 1);
ggml_metal_encoder_set_buffer(enc, ggml_metal_get_buffer_id(op->src[1]), 2);
ggml_metal_encoder_set_buffer(enc, ggml_metal_get_buffer_id(op), 3);
// Dispatch: ne01 rows, ceil(ne1/BATCH_SIZE) token batches, ne02 sequences
// Each threadgroup has BATCH_SIZE threads, each handling one token
const int n_token_batches = (ne1 + BATCH_SIZE - 1) / BATCH_SIZE;
ggml_metal_encoder_dispatch_threadgroups(enc, ne01, n_token_batches, ne02, BATCH_SIZE, 1, 1);
} else {
auto pipeline = ggml_metal_library_get_pipeline_ssm_conv(lib, op);
ggml_metal_encoder_set_pipeline(enc, pipeline);
ggml_metal_encoder_set_bytes(enc, &args, sizeof(args), 0);
ggml_metal_encoder_set_buffer(enc, ggml_metal_get_buffer_id(op->src[0]), 1);
ggml_metal_encoder_set_buffer(enc, ggml_metal_get_buffer_id(op->src[1]), 2);
ggml_metal_encoder_set_buffer(enc, ggml_metal_get_buffer_id(op), 3);
ggml_metal_encoder_dispatch_threadgroups(enc, ne01, ne1, ne02, 1, 1, 1);
}
return 1;
}

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@ -2343,7 +2343,102 @@ kernel void kernel_ssm_conv_f32_f32_4(
x[0] = sumf;
}
constant short FC_ssm_conv_bs [[function_constant(FC_SSM_CONV + 0)]];
// Batched version: each threadgroup processes multiple tokens for better efficiency
// Thread layout: each thread handles one token, threadgroup covers BATCH_SIZE tokens
kernel void kernel_ssm_conv_f32_f32_batched(
constant ggml_metal_kargs_ssm_conv & args,
device const void * src0,
device const void * src1,
device float * dst,
uint3 tgpig[[threadgroup_position_in_grid]],
uint3 tpitg[[thread_position_in_threadgroup]],
uint3 ntg[[threads_per_threadgroup]]) {
// tgpig.x = row index (ir)
// tgpig.y = batch of tokens (i2_base / BATCH_SIZE)
// tgpig.z = sequence index (i3)
// tpitg.x = thread within batch (0..BATCH_SIZE-1)
const short BATCH_SIZE = FC_ssm_conv_bs;
const int64_t ir = tgpig.x;
const int64_t i2_base = tgpig.y * BATCH_SIZE;
const int64_t i3 = tgpig.z;
const int64_t i2_off = tpitg.x;
const int64_t i2 = i2_base + i2_off;
const int64_t nc = args.ne10; // conv kernel size (typically 4)
const int64_t n_t = args.ne1; // number of tokens
// Bounds check for partial batches at the end
if (i2 >= n_t) {
return;
}
// Load conv weights (shared across all tokens for this row)
device const float * c = (device const float *) ((device const char *) src1 + ir*args.nb11);
// Load source for this specific token
device const float * s = (device const float *) ((device const char *) src0 + ir*args.nb01 + i2*args.nb00 + i3*args.nb02);
// Output location for this token
device float * x = (device float *) ((device char *) dst + ir*args.nb0 + i2*args.nb1 + i3*args.nb2);
float sumf = 0.0f;
for (int64_t i0 = 0; i0 < nc; ++i0) {
sumf += s[i0] * c[i0];
}
x[0] = sumf;
}
kernel void kernel_ssm_conv_f32_f32_batched_4(
constant ggml_metal_kargs_ssm_conv & args,
device const void * src0,
device const void * src1,
device float * dst,
uint3 tgpig[[threadgroup_position_in_grid]],
uint3 tpitg[[thread_position_in_threadgroup]],
uint3 ntg[[threads_per_threadgroup]]) {
// tgpig.x = row index (ir)
// tgpig.y = batch of tokens (i2_base / BATCH_SIZE)
// tgpig.z = sequence index (i3)
// tpitg.x = thread within batch (0..BATCH_SIZE-1)
const short BATCH_SIZE = FC_ssm_conv_bs;
const int64_t ir = tgpig.x;
const int64_t i2_base = tgpig.y * BATCH_SIZE;
const int64_t i3 = tgpig.z;
const int64_t i2_off = tpitg.x;
const int64_t i2 = i2_base + i2_off;
const int64_t nc = args.ne10; // conv kernel size (typically 4)
const int64_t n_t = args.ne1; // number of tokens
// Bounds check for partial batches at the end
if (i2 >= n_t) {
return;
}
// Load conv weights (shared across all tokens for this row)
device const float4 * c = (device const float4 *) ((device const char *) src1 + ir*args.nb11);
// Load source for this specific token
device const float4 * s = (device const float4 *) ((device const char *) src0 + ir*args.nb01 + i2*args.nb00 + i3*args.nb02);
// Output location for this token
device float * x = (device float *) ((device char *) dst + ir*args.nb0 + i2*args.nb1 + i3*args.nb2);
float sumf = 0.0f;
for (int64_t i0 = 0; i0 < nc/4; ++i0) {
sumf += dot(s[i0], c[i0]);
}
x[0] = sumf;
}
// ref: ggml.c:ggml_compute_forward_ssm_scan_f32, Mamba-2 part
// Optimized version: reduces redundant memory loads by having one thread load shared values
kernel void kernel_ssm_scan_f32(
constant ggml_metal_kargs_ssm_scan & args,
device const void * src0,
@ -2363,7 +2458,15 @@ kernel void kernel_ssm_scan_f32(
uint3 tgpg[[threadgroups_per_grid]]) {
constexpr short NW = N_SIMDWIDTH;
shared[tpitg.x] = 0.0f;
// Shared memory layout:
// [0..sgptg*NW-1]: partial sums for reduction (existing)
// [sgptg*NW..sgptg*NW+sgptg-1]: pre-computed x_dt values for each token in batch
// [sgptg*NW+sgptg..sgptg*NW+2*sgptg-1]: pre-computed dA values for each token in batch
threadgroup float * shared_sums = shared;
threadgroup float * shared_x_dt = shared + sgptg * NW;
threadgroup float * shared_dA = shared + sgptg * NW + sgptg;
shared_sums[tpitg.x] = 0.0f;
const int32_t i0 = tpitg.x;
const int32_t i1 = tgpig.x;
@ -2403,32 +2506,47 @@ kernel void kernel_ssm_scan_f32(
for (int i2 = 0; i2 < n_t; i2 += sgptg) {
threadgroup_barrier(mem_flags::mem_threadgroup);
for (int t = 0; t < sgptg && i2 + t < n_t; t++) {
const float dt0 = dt[0];
// Pre-compute x_dt and dA for this batch of tokens
// Only first sgptg threads do the loads and expensive math
if (i0 < sgptg && i2 + i0 < n_t) {
// ns12 and ns21 are element strides (nb12/nb10, nb21/nb20)
device const float * x_t = x + i0 * args.ns12;
device const float * dt_t = dt + i0 * args.ns21;
const float dt0 = dt_t[0];
const float dtsp = dt0 <= 20.0f ? log(1.0f + exp(dt0)) : dt0;
const float x_dt = x[0] * dtsp;
const float dA = exp(dtsp * A0);
shared_x_dt[i0] = x_t[0] * dtsp;
shared_dA[i0] = dtsp; // Store dtsp, compute exp(dtsp * A0) per-thread since A0 varies
}
threadgroup_barrier(mem_flags::mem_threadgroup);
for (int t = 0; t < sgptg && i2 + t < n_t; t++) {
const float x_dt = shared_x_dt[t];
const float dA = exp(shared_dA[t] * A0);
s = (s0 * dA) + (B[i0] * x_dt);
const float sumf = simd_sum(s * C[i0]);
if (tiisg == 0) {
shared[t*NW + sgitg] = sumf;
shared_sums[t*NW + sgitg] = sumf;
}
// recurse
s0 = s;
x += args.ns12;
dt += args.ns21;
B += args.ns42;
C += args.ns52;
}
// Advance pointers for next batch
x += sgptg * args.ns12;
dt += sgptg * args.ns21;
threadgroup_barrier(mem_flags::mem_threadgroup);
const float sumf = simd_sum(shared[sgitg*NW + tiisg]);
const float sumf = simd_sum(shared_sums[sgitg*NW + tiisg]);
if (tiisg == 0 && i2 + sgitg < n_t) {
y[sgitg*nh*nr] = sumf;