I. ccache — Compiler Cache (编译缓存)#

ccache wraps your compiler (gcc, g++, nvcc) and caches object files. Same source + same flags = instant replay, no recompilation.

1. How It Works (工作原理)#

$\text{Cache Key (缓存键)} = \text{Hash}(\text{source content} + \text{flags} + \text{compiler version} + \text{headers})$

On a hit (命中): return cached .o file immediately. On a miss (未命中): compile normally, store result.

Two modes: Direct mode (直接模式) — fastest, hashes source directly. Preprocessed mode (预处理模式) — slower, more accurate, used as fallback.

2. Installation (无root安装)#

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# Download & link
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wget https://github.com/ccache/ccache/releases/download/v4.10.2/ccache-4.10.2-linux-x86_64.tar.xz
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tar xf ccache-4.10.2-linux-x86_64.tar.xz -C $HOME/local
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ln -s $HOME/local/ccache-4.10.2-linux-x86_64/ccache $HOME/.local/bin/ccache
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echo 'export PATH="$HOME/.local/bin:$PATH"' >> ~/.bashrc && source ~/.bashrc

3. Integration (接入构建系统)#

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# CMake projects
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cmake -DCMAKE_C_COMPILER_LAUNCHER=ccache \
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      -DCMAKE_CXX_COMPILER_LAUNCHER=ccache \
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      -DCMAKE_CUDA_COMPILER_LAUNCHER=ccache ..
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# pip installs (e.g. vLLM)
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export CMAKE_C_COMPILER_LAUNCHER=ccache
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export CMAKE_CXX_COMPILER_LAUNCHER=ccache
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export CMAKE_CUDA_COMPILER_LAUNCHER=ccache
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pip install -e .

4. Reading Stats (读懂统计)#

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ccache -s

Field	Meaning
Hits = 0% on 1st build	Normal — cache is cold (冷缓存), next build hits ~100%
Hits = 0% on 2nd build	ccache not intercepting — check `CMAKE_*_LAUNCHER`
Cleanups: 240	Cache limit too small → run `ccache --max-size=20G`

5. HPC-Specific Tips (HPC注意事项)#

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# Avoid $HOME quota — move cache to scratch (临时文件系统)
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export CCACHE_DIR=/scratch/$USER/.ccache
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# Normalize absolute paths across nodes (跨节点路径归一化)
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export CCACHE_BASEDIR=$HOME
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# Increase size limit (扩大缓存上限)
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ccache --max-size=20G

6. Quick Reference (命令速查)#

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ccache -s              # stats (统计)
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ccache -z              # reset stats (重置)
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ccache -C              # clear cache (清空)
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CCACHE_DISABLE=1 make  # disable temporarily (临时禁用)