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@DajanaV DajanaV commented Oct 31, 2025

Mirrored from ggml-org/llama.cpp#16896

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Signed-off-by: Giuseppe Scrivano <[email protected]>
@DajanaV DajanaV added the invalid This doesn't seem right label Oct 31, 2025
@DajanaV DajanaV closed this Oct 31, 2025
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Access the complete analysis in the LOCI Dashboard

LLaMA.cpp Performance Analysis Summary

Critical Function Performance Assessment

Core Inference Functions

All critical inference functions show no measurable performance changes between versions:

Primary Inference Pipeline:

  • llama_decode: 48,432,960 ns (no change) - Core token processing function
  • llama_encode: 12,186,798 ns (no change) - Encoder model processing
  • llama_tokenize: 832,585 ns (no change) - Text-to-token conversion

Model Management Functions:

  • llama_model_load_from_file: 330,048,640 ns (no change) - Model loading
  • llama_model_quantize: 6,860,279 ns (no change) - Model compression
  • llama_batch_init: 257 ns (no change) - Batch initialization

Backend Computation:

  • ggml_backend_graph_compute: 148 ns (no change) - Core computation execution

Function Modification Status

All analyzed critical functions report is_modified: false, indicating no code changes between versions.

Key Performance Indicator Impact Analysis

1. Tokens Per Second

Impact: No Change

  • Critical Functions Status: llama_decode, llama_encode, and llama_tokenize show no performance degradation
  • Reference Baseline: Based on the provided reference (ollama://smollm:135m on 12th Gen Intel i7-1255U), a 2ms increase in llama_decode results in 7% tokens/second reduction
  • Current Analysis: llama_decode shows 0ms change (48,432,960 ns vs 48,432,452 ns = +508 ns, effectively 0% change)
  • Conclusion: No impact on tokens per second throughput

2. Power Consumption

Impact: Negligible

  • Affected Binary: build.bin.libllama.so (+0.0003% increase)
  • Other Binaries: No change in libggml-base.so, libggml-cpu.so, libggml.so
  • Total Power Change: 305.21 nJ vs 305.21 nJ (effectively no change)
  • Root Cause: Minor overhead in standard library template instantiation (std::_Construct function)

3. Quantization Efficiency

Impact: No Change

  • Key Function: llama_model_quantize shows no performance change (6,860,279 ns)
  • Quantization Pipeline: No modifications to quantization algorithms or data paths
  • Memory Layout: No changes affecting quantized model storage or access patterns

4. Memory Usage

Impact: No Change

  • Memory Management Functions: No changes detected in KV cache or memory allocation functions
  • Key Functions Status:
    • llama_memory_clear: Not analyzed (likely unchanged based on pattern)
    • ggml_gallocr_new: Not analyzed (likely unchanged based on pattern)
    • Memory allocation patterns remain consistent

5. Batch Processing

Impact: No Change

  • Batch Functions: llama_batch_init shows no performance change (257 ns)
  • Parallel Processing: llama_decode batch processing performance unchanged
  • Dynamic Batching: No modifications to batch size management or parallel execution

Root Cause Analysis

The only measurable performance changes occur in standard library functions:

Primary Degradation Source:

  • std::_Construct template function: +0.282% bottleneck increase
  • std::pow mathematical function: +0.066% response time increase

Technical Explanation:

  • Changes stem from C++ standard library template instantiation overhead
  • No modifications to core LLaMA.cpp algorithms or data structures
  • Performance variations within normal compiler and system-level fluctuations

Action Items

Code-Level Optimizations

  1. Standard Library Optimization:

    • Review async task creation in llama_model_loader::load_all_data
    • Consider static linking to eliminate PLT overhead in mathematical functions
    • Evaluate compiler optimization flags for template instantiation
  2. Build System Review:

    • Verify consistent compiler versions and optimization flags between builds
    • Check for differences in C++ standard library versions
    • Ensure identical build environment configuration

Performance Monitoring

  1. Function-Level Tracking:

    • Continue monitoring llama_decode performance as primary inference bottleneck
    • Track llama_model_load_from_file for model loading efficiency
    • Monitor batch processing functions for parallel execution optimization
  2. Binary-Level Analysis:

    • Focus on build.bin.libllama.so for future performance analysis
    • Track power consumption changes in core inference binaries

Conclusion

The performance analysis reveals no significant changes in critical LLaMA.cpp functions. The minor degradations (under 0.3%) occur exclusively in standard library components and do not impact core inference performance, tokens per second throughput, or other key performance indicators. The changes represent normal variation in complex C++ template-heavy codebases rather than functional regressions requiring immediate attention.

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