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强力提高 android 4 编译效率(c,c++部分)

13-01-19

Setting up ccacheYou can optionally tell the build to use the ccache compilation tool. Ccache acts as a compiler cache that can be used to speed-up rebuilds. This works...

Setting up ccache
You can optionally tell the build to use the ccache compilation tool. Ccache acts as a compiler cache that can be used to speed-up rebuilds. This works very well if you do "make clean" often, or if you frequently switch between different build products.
 
Put the following in your .bashrc or equivalent.
 
export USE_CCACHE=1
By default the cache will be stored in ~/.ccache. If your home directory is on NFS or some other non-local filesystem, you will want to specify the directory in your .bashrc as well.
 
export CCACHE_DIR=<path-to-your-cache-directory>
The suggested cache size is 50-100GB. You will need to run the following command once you have downloaded the source code:
 
prebuilts/misc/linux-x86/ccache/ccache -M 50G
When building Ice Cream Sandwich (4.0.x) or older, ccache is in a different location:
 
prebuilt/linux-x86/ccache/ccache -M 50G
This setting is stored in the CCACHE_DIR and is persistent.
 
 
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原理:
 
ccache的使用方式,可以加速我们c与c++的编译速度原理就是中间文件的一个缓存,是同一个.o文件的话就省去再次编译的速度。
介于android中c与c++文件数量能占到刚不到一半,所以这个速度还是能省下很多的。
 
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配置:
1在环境变量里添加:
export USE_CCACHE=1
export CCACHE_DIR=/HDD/.ccache
(环境变量有四个位置添加都有效,我习惯添加到全局用户环境变量配置文件:sudo gedit /etc/profile,
第一个是标志,android编译会检测这个
第二个是缓存路径,默认是~/.ccache)
2随便找一个android工程(可能需要2.3以上),设置缓存的大小(注意每执行一次这个,缓存路径会被初始化一次,所以执行一次就好);
prebuilt/linux-x86/ccache/ccache -M 50G
第一次编译一个工程,会缓存工程.o文件,
第二次提升效果明显
ccache缓存的调用情况执行下面命令监视
$ watch -n1 -d prebuilt/linux-x86/ccache/ccache -s
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真实测试:
工程android 4.0.4
第一次编译:make -j8      36分钟左右;
修改了frameworks的一个资源文件;
再次编译:make clean;make -j8     18分钟
 
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