On 30 January 2014 23:10, Rob Weir <robw...@apache.org> wrote: > On Wed, Jan 29, 2014 at 4:18 AM, Andre Fischer <awf....@gmail.com> wrote: > > I would like to report some observations that I made when thinking about > how > > to make building OpenOffice with one global makefile feasible. It will > > probably the last of build related mails in the near future. > > > > Traditional make uses a top-down approach. It starts with a target, > 'all' > > by default, and looks at its dependencies. When one of those has to be > made > > or is newer then the target then the target also has to be made. This is > > done recursively and depth-first. Every file on which 'all' has a > direct or > > indirect dependency has to be checked. If we would build OpenOffice with > > one makefile (included makefiles don't count) then that are a lot of > files > > to check. There are about 9800 cxx files, 3500 c files, 12000 hxx files, > > and lot of external headers. Checking the modification time of so many > > files is one of the reasons for the delay in , say, sw/ between starting > > make and its first action. > > > > As I don't have all global dependencies in a format that would allow > > experimation, I tried how long it would take to get the mtime (time of > last > > modification) for all files, source, generated, compiled, linked, about > > 120000. I wrote a small Java program for that. With a warm cache that > > takes about 23s. When run in 4 threads this reduced to less than 8s. > Could > > be worse. > > > > But it also could be better because in general there are only a few files > > modified, usually files that you modified yourself in an editor. There > is > > another approach, introduced, as far as I know, by the tup [1] build > tool, > > that is bottom up. If you had something similar to the oracle of > complexity > > theory, that gave you the list of modified files since the last build, > you > > could find the depending files much faster. Faster for two reasons. > > Firstly, there is only one path in the dependency tree up towards the > root > > (while there are many down from the root). Only targets on this path are > > affected by the modified file. Secondly, the dependency analysis is > > comparatively cheap. The expensive part is to determine the file > > modification times. If they where miraculously given then even the > top-down > > approach would not take noticably longer. > > > > So I made another experiment to see if such an oracle can be created. > Java > > 7 has the java.nio.file.WatchService that lets you monitor file > > modfifications in one directory. I registered it to all directories in > our > > source tree (some 16000 directories). With the WatchService in place > every > > file modification can be recorded and stored for later. On the next > build > > you only have to check the set of modified files, not all files. > > Registering the directory watchers takes a couple of seconds but after > that > > it does not cause any noticeable CPU activity. Any file modifications are > > reported almost at once. I do not have the framework in place to start a > > build with this information but I would expect it to be as fast as > compiling > > the modified files and linking takes. > > > > The tup website references a paper [2] in which the established top-down > > approaches are called alpha alogithms and the new bottom-up approach is > > called beta algorithm. Tup has implemented a file modification watcher > (in C > > or C++) only for Linux. On Windows it just scans all files (for which it > > needs a little more time than my Java program, maybe it does not use more > > than one thread). > > > > > > This is something that we should keep in mind for when we ever should > get a > > build solution with global dependencies and this build tool would turn > out > > to be too slow. > > > > > > If can find the source code of my Java experiments at [3]. If nothing > else > > you can see an application of the ForkJoinPool that allowed my to write > the > > parallel file system scan in just a few lines. There is also an > alternative > > implementation that uses the ExecutorService (with a fixed thread pool) > > which needs a few more lines of code. And there is of course the use of > the > > WatchService. > > > > Has anyone read this book? > > http://www.amazon.com/Large-Scale-Software-Design-John-Lakos/dp/0201633620 > > It was on my list to read for many years. From what I've seen it > suggests design approaches to the improve build times. So things that > go beyond what you can do by just changing build files, more > fundamental changes to how interfaces are defined. >
Have read it, the book goes more into C++ structures and design, than the actual build process. If you have a pure C++ project, you can do a lot of speed improvement by definining the classes for speed instead of purity. Its quite a good book, but have very little for the AOO build system. > > Otherwise I wonder if we're trying to optimize a bubble sort? > No we are trying to moving away from 3-4 build components trying to do the same thing and each sub-optimized. In other words, our system has grown complex, it was not designed complex. Just look at how different the single module makefiles are (should have been standardized) and at the same time we have central modules that have a hefty number of "if" because of the lacking standard. I know its unpopular to write it, but AOO is by no means a REAL BIG software package...it just looks that way. Building a linux system is a factor 4-5 to AOO, building microsoft MFC (for those who have access) is about 1.5. Of course depending how you look at it. rgds jan I. > > -Rob > > > > > Regards, > > Andre > > > > > > [1] http://gittup.org/tup/ > > [2] http://gittup.org/tup/build_system_rules_and_algorithms.pdf > > [3] http://people.apache.org/~af/test.zip > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: dev-unsubscr...@openoffice.apache.org > > For additional commands, e-mail: dev-h...@openoffice.apache.org > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@openoffice.apache.org > For additional commands, e-mail: dev-h...@openoffice.apache.org > >
