Difference between revisions of "Ccache"
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To configure Mozilla builds to use ccache, you'll need to configure some make and configure options. In your ''.mozconfig'', add the following: | To configure Mozilla builds to use ccache, you'll need to configure some make and configure options. In your ''.mozconfig'', add the following: | ||
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ac_add_options --with-ccache=/usr/bin/ccache | ac_add_options --with-ccache=/usr/bin/ccache | ||
Revision as of 23:28, 11 August 2011
ccache is a compiler cache for C and C++. It does what its function implies: caches the results of compilations. The net result: builds are faster!
Contents
Installing
ccache is typically available in your operating system's package manager of choice.
On Mac:
$ brew install ccache
On Ubuntu:
$ apt-get install ccache
Configuring ccache
By default, ccache will put its cache in ~/.ccache. You can verify this by running:
$ ccache -s
That prints out the location of the current cache with some statistics.
You can modify the location of the cache via environment variables such as CCACHE_DIR. For more, see the man page (man ccache).
Like most anything that is I/O bound, ccache will benefit from having its cache on a fast I/O device, like an SSD. If you can, configure your cache to run off the fastest device you can. If you are using magnetic storage, put the cache on a separate spindle from the source tree you are building.
For example,
$ export CCACHE_DIR=/Volumes/Scratch/ccache
The default cache size is 1GB. A typical mozilla-central build of Firefox will fully saturate a cache of this size, evicting entries and thus lowering cache hit rate. You can modify the cache size as follows:
$ ccache --max-size 2GB
Configuring Mozilla Builds
To configure Mozilla builds to use ccache, you'll need to configure some make and configure options. In your .mozconfig, add the following:
ac_add_options --with-ccache=/usr/bin/ccache
Be sure to specify the appropriate path to ccache on your system!
Now, run a build and verify the cache is being utilized:
$ ccache -s cache directory /home/gps/.ccache cache hit (direct) 0 cache hit (preprocessed) 0 cache miss 0 files in cache 0 cache size 0 Kbytes max cache size 2.0 Gbytes $ make -f client.mk build # in another shell, after the build has churned for a while: $ ccache -s cache directory /home/gps/.ccache cache hit (direct) 2 cache hit (preprocessed) 7 cache miss 2044 called for link 27 preprocessor error 1 unsupported source language 1 autoconf compile/link 19 unsupported compiler option 4 files in cache 6226 cache size 659.0 Mbytes max cache size 2.0 Gbytes
Sample Performance Impact
The following lists sample impact of ccache on build times. The first build should be ran with ccache enabled, but an empty cache. The second build should be executed after a distclean.
| System Description | Build Type | First Build (Empty Cache) | Second Build (Populated Cache) | Change |
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