AOSP 8.1编译时ccache设为30GB却始终不超过1GB的技术咨询

Let's break down the possible reasons why your ccache isn't growing beyond 1GB despite setting a 30GB limit, and walk through practical fixes for each scenario:

1. Verify ccache Configuration in the Container #

First, confirm that your max size setting is actually active inside the Docker container:

• Enter your running container with docker exec -it <container-name> /bin/bash
• Run ccache -p and look for the max_size entry. If it shows 1GB instead of 30GB, your configuration isn't taking effect.

Fixes for Configuration Issues: #

• Set the max size directly in the container: Run ccache -M 30G to enforce the limit immediately.
• Align the config file with your mounted directory: ccache reads config from ~/.ccache/ccache.conf by default. Since you're mounting /home/builder/ccache/, either:
  • Move your ccache.conf into this mounted directory and set the environment variable: export CCACHE_CONFIGPATH=/home/builder/ccache/ccache.conf
  • Add the max size line directly to the config file: echo "max_size = 30G" >> /home/builder/ccache/ccache.conf

2. Check Host Disk Space & Quotas #

Even if the container's ccache is set to 30GB, the host system might be limiting the space:

• On your host machine, run df -h /path/to/your/host/ccache-directory to check available space on the partition where your ccache is mounted. Make sure there's at least 30GB of free space here.
• Check if disk quotas are enabled for the user owning the host ccache directory: Run quota -u <your-host-username> to see if a quota cap is restricting growth.

3. Confirm AOSP Build Environment Variables #

AOSP's build scripts might be overriding your ccache settings:

• Before starting the build, explicitly set these variables in the container to ensure they take priority:

  export USE_CCACHE=1
  export CCACHE_DIR=/home/builder/ccache/
  export CCACHE_MAXSIZE=30G
  

• You can also add these lines to the builder user's ~/.bashrc or ~/.profile in the container to make them persistent across sessions.

4. Check Directory Permissions #

If the builder user inside the container doesn't have write access to the mounted ccache directory, ccache can't store more cache:

• In the container, run ls -ld /home/builder/ccache/ to check permissions. The output should show read/write access for the builder user (uid/gid matching the container's user).
• If permissions are incorrect, fix them on the host: chown -R <host-uid>:<host-gid> /path/to/host/ccache (match the uid/gid of the builder user in the container) or adjust them inside the container with sudo chown -R builder:builder /home/builder/ccache/.

5. Check for ccache Version Bugs #

Ubuntu 16.04 ships with ccache 3.2.4, which has known issues with large max size settings in some scenarios. Try upgrading to a newer version:

• Inside the container, install dependencies first: sudo apt-get install autoconf automake libtool
• Download and compile the latest stable ccache release (e.g., 4.8.3):

  wget https://github.com/ccache/ccache/releases/download/v4.8.3/ccache-4.8.3.tar.xz
  tar xvf ccache-4.8.3.tar.xz
  cd ccache-4.8.3
  ./configure
  make
  sudo make install
  

• Verify the new version with ccache --version and re-test your build.

After trying these steps, run watch ccache -s again during your AOSP build—you should see the cache size start growing towards the 30GB limit as more objects are compiled and cached.

内容的提问来源于stack exchange，提问作者Slaviro