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The boost and jack2 packages fail to build when PARALLEL_JOBS is empty so instead of using an empty PARALLEL_JOBS don't use it in the MAKE variable when top-level parallel make is being used. To simplify the use of top-level parallel make, check the MAKEFLAGS variable to know automatically if the -j option is being used, also use the "=" operator instead of the ":=" operator because the MAKEFLAGS variable can be checked only in a "recursively expanded variable". The "override" keyword must be used in order to change the automatic variable "MAKE". When the top-parallel make is being used the sub-make are called without specifying the "-j" option in order to let GNU make share the job slots specified in the top make. This is done because GNU make is able to share the job slots available between each instance of make so if you want to increase the number of jobs you just need to increase the <jobs> value in the top make -j<jobs> command. If we specify the -j<jobs> option in each instance of make, it is less efficient, e.g. in a processor with 8 cores we specify -j9 in each instance: the number of processes goes up to 81 because each sub-make can execute 9 processes. The excessive number of processes is not a good thing because in my tests even -j16 is slower than -j9. Instead if we don't specify the -j<jobs> option in the sub-make, the top make share the job slots automatically between each instance, so the number of process in this examples goes up to 9 that is faster than using up to 81 processes. e.g. when the -j3 option is specified only in the top make: possible state n. 1: process 1 - <packagea>-build process 2 - <packagea>-build process 3 - <packagea>-build possible state n. 2: process 1 - <packagea>-extract process 2 - <packageb>-configure process 3 - <packagec>-build possible state n. 3: process 1 - <packagea>-build make -j1 process 2 - <packageb>-build make -j1 process 3 - <packagec>-build make -j1 Signed-off-by: Fabio Porcedda <fabio.porcedda@gmail.com> Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> |
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| arch | ||
| board | ||
| boot | ||
| configs | ||
| docs | ||
| fs | ||
| linux | ||
| package | ||
| support | ||
| system | ||
| toolchain | ||
| .defconfig | ||
| .gitignore | ||
| CHANGES | ||
| Config.in | ||
| Config.in.legacy | ||
| COPYING | ||
| Makefile | ||
| Makefile.legacy | ||
| README | ||
Buildroot is a simple, efficient and easy-to-use tool to generate embedded Linux systems through cross-compilation. The documentation can be found in docs/manual. You can generate a text document with 'make manual-text' and read output/docs/manual/manual.text. Online documentation can be found at http://buildroot.org/docs.html To build and use the buildroot stuff, do the following: 1) run 'make menuconfig' 2) select the target architecture and the packages you wish to compile 3) run 'make' 4) wait while it compiles 5) find the kernel, bootloader, root filesystem, etc. in output/images You do not need to be root to build or run buildroot. Have fun! Buildroot comes with a basic configuration for a number of boards. Run 'make list-defconfigs' to view the list of provided configurations. Please feed suggestions, bug reports, insults, and bribes back to the buildroot mailing list: buildroot@buildroot.org You can also find us on #buildroot on Freenode IRC.