llama: avoid copying logits during prompt decode in MTP (#23198)

* llama: avoid copying logits during prompt decode in MTP

* review: update comment

* llama-graph: call set_output for t_h_pre_norm
This commit is contained in:
Aman Gupta
2026-05-17 23:30:25 +08:00
committed by GitHub
parent 39cf5d6191
commit 3e12fbdea5
10 changed files with 91 additions and 27 deletions
+37 -14
View File
@@ -895,8 +895,17 @@ float * llama_context::get_embeddings_pre_norm_ith(int32_t i) {
throw std::runtime_error("no pre-norm embeddings");
}
const int64_t j = output_resolve_row(i);
const uint32_t n_embd = model.hparams.n_embd;
if (!cparams.embeddings_pre_norm_masked) {
// unmasked: pre-norm rows are stored densely, indexed by raw token position.
if (i < 0 || (size_t)(i + 1) * n_embd > embd_pre_norm.size) {
throw std::runtime_error(format("out of range [0, %zu)", embd_pre_norm.size / n_embd));
}
return embd_pre_norm.data + (size_t) i * n_embd;
}
const int64_t j = output_resolve_row(i);
return embd_pre_norm.data + j*n_embd;
} catch (const std::exception & err) {
LLAMA_LOG_ERROR("%s: invalid pre-norm embeddings id %d, reason: %s\n", __func__, i, err.what());
@@ -1088,10 +1097,11 @@ void llama_context::set_embeddings(bool value) {
//sched_need_reserve = true;
}
void llama_context::set_embeddings_pre_norm(bool value) {
LLAMA_LOG_DEBUG("%s: value = %d\n", __func__, value);
void llama_context::set_embeddings_pre_norm(bool value, bool masked) {
LLAMA_LOG_DEBUG("%s: value = %d, masked = %d\n", __func__, value, masked);
cparams.embeddings_pre_norm = value;
cparams.embeddings_pre_norm = value;
cparams.embeddings_pre_norm_masked = masked;
}
void llama_context::set_causal_attn(bool value) {
@@ -1737,6 +1747,7 @@ int llama_context::decode(const llama_batch & batch_inp) {
};
int64_t n_outputs_prev = 0;
int64_t n_tokens_prev = 0;
do {
const auto & ubatch = mctx->get_ubatch();
@@ -1882,16 +1893,21 @@ int llama_context::decode(const llama_batch & batch_inp) {
// extract pre-norm embeddings (hidden state before the final output norm)
// only meaningful in LLAMA_POOLING_TYPE_NONE (per-token); other pooling modes are ignored.
if (embd_pre_norm.data && t_h_pre_norm && n_outputs > 0 && cparams.pooling_type == LLAMA_POOLING_TYPE_NONE) {
ggml_backend_t backend_h = ggml_backend_sched_get_tensor_backend(sched.get(), t_h_pre_norm);
GGML_ASSERT(backend_h != nullptr);
{
const bool masked = cparams.embeddings_pre_norm_masked;
const int64_t n_rows = masked ? n_outputs : (int64_t) ubatch.n_tokens;
const int64_t offset = masked ? n_outputs_prev : n_tokens_prev;
const uint32_t n_embd = hparams.n_embd;
float * embd_pre_norm_out = embd_pre_norm.data + n_outputs_prev*n_embd;
if (embd_pre_norm.data && t_h_pre_norm && n_rows > 0 && cparams.pooling_type == LLAMA_POOLING_TYPE_NONE) {
ggml_backend_t backend_h = ggml_backend_sched_get_tensor_backend(sched.get(), t_h_pre_norm);
GGML_ASSERT(backend_h != nullptr);
GGML_ASSERT( n_outputs_prev + n_outputs <= n_outputs_all);
GGML_ASSERT((n_outputs_prev + n_outputs)*n_embd <= (int64_t) embd_pre_norm.size);
ggml_backend_tensor_get_async(backend_h, t_h_pre_norm, embd_pre_norm_out, 0, n_outputs*n_embd*sizeof(float));
const uint32_t n_embd = hparams.n_embd;
float * embd_pre_norm_out = embd_pre_norm.data + offset*n_embd;
GGML_ASSERT((offset + n_rows)*n_embd <= (int64_t) embd_pre_norm.size);
ggml_backend_tensor_get_async(backend_h, t_h_pre_norm, embd_pre_norm_out, 0, n_rows*n_embd*sizeof(float));
}
}
// Copy backend sampling output if this ubatch produced any sampling tensors.
@@ -1908,6 +1924,7 @@ int llama_context::decode(const llama_batch & batch_inp) {
}
n_outputs_prev += n_outputs;
n_tokens_prev += ubatch.n_tokens;
} while (mctx->next());
// set to total number of outputs in the batch, for use in llama_get_logits_ith
@@ -1999,6 +2016,12 @@ uint32_t llama_context::output_reserve(int32_t n_outputs) {
embd.size = has_embd ? n_embd_out*n_outputs_max : 0;
embd_pre_norm.size = has_embd_pre_norm ? n_embd*n_outputs_max : 0;
if (has_embd_pre_norm && !cparams.embeddings_pre_norm_masked) {
// unmasked: pre-norm row exists for every token in the batch, not just
// those flagged via batch.logits[i] -> size by token count instead.
embd_pre_norm.size = (size_t) n_embd * n_batch;
}
// Allocate backend sampling output buffers if there are backend samplers configured.
const bool has_sampling = !sampling.samplers.empty();
if (has_sampling) {
@@ -3547,8 +3570,8 @@ float * llama_get_embeddings_seq(llama_context * ctx, llama_seq_id seq_id) {
return ctx->get_embeddings_seq(seq_id);
}
void llama_set_embeddings_pre_norm(llama_context * ctx, bool value) {
ctx->set_embeddings_pre_norm(value);
void llama_set_embeddings_pre_norm(llama_context * ctx, bool value, bool masked) {
ctx->set_embeddings_pre_norm(value, masked);
}
float * llama_get_embeddings_pre_norm(llama_context * ctx) {