On 7-12-2016 17:46, Gregory Farnum wrote: > On Wed, Dec 7, 2016 at 1:26 AM, Willem Jan Withagen <wjw@xxxxxxxxxxx> wrote: >> On 7-12-2016 01:09, Gregory Farnum wrote: >>> The default (or at least, ./do_cmake.sh-setup) Ceph build makes use of >>> cmake. This is nice for speeding up builds, but as the amount of disk >>> space increases it really explodes disk usage on dev boxes. As of >>> today, a Ceph repo with build artifacts is ~30GB, and my ccache >>> directory is ~32GB. >>> >>> For me and many of the other Red Hat devs, that's a significant >>> fraction of the 256GB available on our (shared box) home-dir SSDs, and >>> I don't think there's *too* much advantage to be gained by giving each >>> dev their own ccache dir. If anybody has expertise configuring ccache >>> and wants to tweak our build scripts to make setting that up easy, >>> it'd be cool — I started in on the ccache man page and it doesn't look >>> too hard but I've never configured any of it. Created a ticket at >>> http://tracker.ceph.com/issues/18160 >> >> From the ccache site: >> "Another reason to use ccache is that the same cache is used for builds >> in different directories. If you have several versions or branches of a >> software stored in different directories, many of the object files in a >> build directory can probably be taken from the cache even if they were >> compiled for another version or branch >> " >> >> So why not have a shared/global ccache. I would expect the larger part >> of the project to generate the same code over and over for most of the >> users? On average only a small fraction of the compile is different >> between developers, and even that will be absorbed by a large general >> cache. The trick with a cache is that the benifits increase if there are >> more users doing/reusing more of the same. So the advantage of 300G >> cache is better that 10*30G. Note that ccache can even compress data in >> the cache, leading to even more objects in your cache. With an even >> better hit ratio. >> >> Get ride of all personal ccache.conf files and >> in global /etc/ccache.conf >> cache_dir = /somewhere/you/want/then/ccache >> max_size = as large as possible >> umask = 777 >> # or 775 if devs are all in the same group. > > Yes, something like this would be involved too. But if you grep for > ccache in ceph.git you'll notice it's doing some level of autoconfig — > I don't know how much — which needs to play nicely as well. > Now that I look at it with fresh eyes it looks like maybe our tooling > is only invoking ccache and we do just need the config; I'm just a > little fidgety about it because some of the test-dir contents are > referencing specific directories and I'm not sure if we invoke any of > those bits via make check or similar. Well, these are all references to ccache in the Cmake sources: ./src/CMakeLists.txt:693:if (WITH_CCACHE AND CCACHE_FOUND) ./src/CMakeLists.txt:694: list(APPEND ROCKSDB_CMAKE_ARGS -DCMAKE_CXX_COMPILER=ccache) ./src/CMakeLists.txt:696:else(WITH_CCACHE AND CCACHE_FOUND) ./src/CMakeLists.txt:698:endif(WITH_CCACHE AND CCACHE_FOUND) This^^^^^^ is code for rocksdb to use ccache, so nothing there. ./CMakeLists.txt:40:option(WITH_CCACHE "Build with ccache.") ./CMakeLists.txt:41:if(WITH_CCACHE) ./CMakeLists.txt:42: find_program(CCACHE_FOUND ccache) ./CMakeLists.txt:43: if(CCACHE_FOUND) ./CMakeLists.txt:44: message(STATUS "Building with ccache: ${CCACHE_FOUND}, CCACHE_DIR=$ENV{CCACHE_DIR}") ./CMakeLists.txt:45: set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache) ./CMakeLists.txt:46: # ccache does not accelerate link (ld), but let it handle it. by passing it ./CMakeLists.txt:49: set_property(GLOBAL PROPERTY RULE_LAUNCH_LINK ccache) ./CMakeLists.txt:50: else(CCACHE_FOUND) ./CMakeLists.txt:51: message(FATAL_ERROR "Can't find ccache. Is it installed?") ./CMakeLists.txt:52: endif(CCACHE_FOUND) ./CMakeLists.txt:53:endif(WITH_CCACHE) This^^^^ is code to educate Cmake to use ccache as compiler/linker.... So nothing scary there... And in the *.sh files is the only real reference to ccache: ./src/test/docker-test-helper.sh:119: local ccache ./src/test/docker-test-helper.sh:120: mkdir -p $HOME/.ccache ./src/test/docker-test-helper.sh:121: ccache="--volume $HOME/.ccache:$HOME/.ccache" ./src/test/docker-test-helper.sh:123: local cmd="docker run $opts --rm --name $image --privileged $ccache" And I known nothing of docker, but it's use seems to override the global cache. And could deserve a bit of rewrite if this access is actually intended to use the cache that is build outside of the docker. Perhaps ask Loic. But other than that I was not able to find references to ccache. --WjW -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
