On 2015/02/03 15:24, Mike Hommey wrote: > On Tue, Feb 03, 2015 at 02:27:52PM +0900, ISHIKAWA,chiaki wrote: >> I did a non-unified build and saw the expected failure. >> This is a summary of what I saw. >> >> Background: >> >> I may need to modify and debug basic I/O routines on local PC, and so >> want to avoid unnecessary compilation. I use ccache locally to make >> sure I can avoid re-compilation of touched but not modified C++ source >> files (files get touched and remain unmodified when I execute >> "hg qpop" and "hg qpush" in successions to work on different patches. >> Without ccache, I have to compile many files. ccache helps a lot.) >> >> There is a different perspective on unified compilation. >> >> Compiler farm users: >> One time fast compilation　is very important. >> So unified compilation is a win. >> (I suspect precompiled headers, -pch, would be a good win, too.) >> >> Developers who repeats "edit a small set of files, compile and link" >> many times on local PC: >> >> He/she may modify only a few files and want quick >> turn around of the compile of a few files and link time. >> >> Unified compilation actually compiles more lines than he/she wants >> (because of the extra source lines included in unified source files >> in which his/her modified files are also included. >> (Correct? Am I missing something here?) >> So he/she may not like unified compilation in such scenario. > > Here's my take on this: yes, we should optimize for build times when > code is modified. > > But here's the thing: in most directories, unified compilation shouldn't > be making a huge difference. That is, compiling one unified source vs. > compiling one source shouldn't make a big difference. If it does (and it > does in some directories like js/src), then the number of unified > sources in the directory where it's a problem should be adjusted. > > Mike
Mike, thank you for the comment. I suspect this is indeed the case in many directories. (I mean unless a change of a single file caused 20 or 30 files to be included into a unified source, then it is an overhead certainly. But so far, the upper-bound of single change of a file is less than a couple of minutes including the link with -gsplit-dwarf.) I will report if I find a file, when touched, causes an extraordinarily long compilation time (by including many of the source files during unified compilation). By the way, I saw Unified_binding_*.cpp files during compilation, and I suspect they are different types of unified compilation since this "unified_binding" compilation seems to occur no matter what the setting of FILES_PER_UNIFIED_FILE. TIA CI _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
