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The current code spawns as many jobs as up to twice the number of CPUs. On small-class machines like laptops, with a limitted amount of memory, but still a few CPUs (real or hyperthreads), the HDD becomes a bottleneck, and it becomes almost impossible to do anythiong else while there is a build in progress. Limit the number of jobs to the number of CPUs plus one. Even on fast machines with fast HDDs, this settings keeps the machine fully busy (for those packages that can build in parallel, of course). For example, building qemu or the linux kernel kept my hyperthreaded hexa Core i7 with 18GiB of RAM, busy at 99% (I never ever managed to get 100% even with more jobs, not even 200); while on my hyperthreaded dual Core i5 with only 4GiB and a slow HDD, I still topped at 100% CPU, while still able to do some work involving the HDD. If the number of processors is not available, assume one. Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr> Cc: Nathan Lynch <ntl@pobox.com> Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Reviewed-by: Nathan Lynch <ntl@pobox.com> Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
To build and use the buildroot stuff, do the following:
1) run 'make menuconfig'
2) select the packages you wish to compile
3) run 'make'
4) wait while it compiles
5) Use your shiny new root filesystem. Depending on which sort of
root filesystem you selected, you may want to loop mount it,
chroot into it, nfs mount it on your target device, burn it
to flash, or whatever is appropriate for your target system.
You do not need to be root to build or run buildroot. Have fun!
Offline build:
==============
In order to do an offline-build (not connected to the net), fetch all
selected source by issuing a
$ make source
before you disconnect.
If your build-host is never connected, then you have to copy buildroot
and your toplevel .config to a machine that has an internet-connection
and issue "make source" there, then copy the content of your dl/ dir to
the build-host.
Building out-of-tree:
=====================
Buildroot supports building out of tree with a syntax similar
to the Linux kernel. To use it, add O=<directory> to the
make command line, E.G.:
$ make O=/tmp/build
And all the output files (including .config) will be located under /tmp/build.
More finegrained configuration:
===============================
You can specify a config-file for uClibc:
$ make UCLIBC_CONFIG_FILE=/my/uClibc.config
And you can specify a config-file for busybox:
$ make BUSYBOX_CONFIG_FILE=/my/busybox.config
To use a non-standard host-compiler (if you do not have 'gcc'),
make sure that the compiler is in your PATH and that the library paths are
setup properly, if your compiler is built dynamically:
$ make HOSTCC=gcc-4.3.orig HOSTCXX=gcc-4.3-mine
Depending on your configuration, there are some targets you can use to
use menuconfig of certain packages. This includes:
$ make HOSTCC=gcc-4.3 linux-menuconfig
$ make HOSTCC=gcc-4.3 uclibc-menuconfig
$ make HOSTCC=gcc-4.3 busybox-menuconfig
Please feed suggestions, bug reports, insults, and bribes back to the
buildroot mailing list: buildroot@uclibc.org