Re: compile speed
On Sun, Jun 15, 2008 at 07:19:29PM +0200, Hans-J. Ullrich wrote:
> yes, that is the point, I wanted to know. I suppose, higher than "-j 4" will
> let the system make too slow.
>
> Just another last: Are the entries in /etc/apt/apt-build.conf used by any(!)
> compiler applications, which are debian based ? I am thinking especially of
> commands like "make-kpkg", ncurses tools like "module-assistant" and dpkg
> related things, which are executed during upgrading of packages.
The thing is, many Makefiles are NOT proper and will result in broken
builds if you try to run them in parallel. So there is no way you can
just say 'always do this' because sometimes it doesn't work.
I find that 2xCores is a good value, since it tries to make sure each
core has something to compile even while doing disk io for another
compile task. Any more than that never seems to improve things and just
increases the number of context switches that need to be done.
Another option is to look at gcc's -pipe option, which makes it use
pipes with multiple processes rather than temporary files with each
compile step process run in turn. It is completely safe no matter what
the Makefile does, but won't likely gain as much, but still better than
nothing.
--
Len Sorensen
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