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Test-based VRAM scratch size + context adjustment #2056

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Jul 1, 2023
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Test-based VRAM scratch size + context adjustment #2056

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38 changes: 35 additions & 3 deletions llama.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,7 @@ enum e_model {
MODEL_65B,
};

static const size_t kB = 1024;
static const size_t MB = 1024*1024;

// computed for n_ctx == 2048
Expand Down Expand Up @@ -129,6 +130,34 @@ static const std::map<e_model, size_t> & MEM_REQ_EVAL()
return k_sizes;
}

// amount of VRAM needed per batch size to hold temporary results
// the values for 3b and 65b are not derived from testing but instead chosen conservatively
static const std::map<e_model, size_t> & VRAM_REQ_SCRATCH_BASE()
{
static std::map<e_model, size_t> k_sizes = {
{ MODEL_3B, 512ull * kB },
{ MODEL_7B, 512ull * kB },
{ MODEL_13B, 640ull * kB },
{ MODEL_30B, 768ull * kB },
{ MODEL_65B, 1536ull * kB },
};
return k_sizes;
}

// amount of VRAM needed per batch size and context to hold temporary results
// the values for 3b and 65b are not derived from testing but instead chosen conservatively
static const std::map<e_model, size_t> & VRAM_REQ_SCRATCH_PER_CONTEXT()
{
static std::map<e_model, size_t> k_sizes = {
{ MODEL_3B, 128ull },
{ MODEL_7B, 128ull },
{ MODEL_13B, 160ull },
{ MODEL_30B, 208ull },
{ MODEL_65B, 416ull },
};
return k_sizes;
}

// default hparams (LLaMA 7B)
struct llama_hparams {
uint32_t n_vocab = 32000;
Expand Down Expand Up @@ -1112,11 +1141,14 @@ static void llama_model_load_internal(
fprintf(stderr, "%s: not allocating a VRAM scratch buffer due to low VRAM option\n", __func__);
ggml_cuda_set_scratch_size(0); // disable scratch
} else {
vram_scratch = n_batch * MB;
const size_t vram_scratch_base = VRAM_REQ_SCRATCH_BASE().at(model.type);
const size_t vram_scratch_per_context = VRAM_REQ_SCRATCH_PER_CONTEXT().at(model.type);
vram_scratch = n_batch * (vram_scratch_base + n_ctx * vram_scratch_per_context);
ggml_cuda_set_scratch_size(vram_scratch);
if (n_gpu_layers > 0) {
fprintf(stderr, "%s: allocating batch_size x 1 MB = %zd MB VRAM for the scratch buffer\n",
__func__, vram_scratch / MB);
fprintf(stderr, "%s: allocating batch_size x (%zd kB + n_ctx x %zd B) = %zd MB VRAM for the scratch buffer\n",
__func__, vram_scratch_base / kB, vram_scratch_per_context,
(vram_scratch + MB - 1) / MB); // round up
}
}
#endif // GGML_USE_CUBLAS
Expand Down