Re: [gentoo-user] make -j <n> for kernel builds?

[Alan McKinnon]

On 31/10/2016 23:57, John Covici wrote:
> On Mon, 31 Oct 2016 13:37:50 -0400,
> Meino.Cramer@×××.de wrote:
>>
>> Dale <rdalek1967@×××××.com> [16-10-31 18:36]:
>>> Meino.Cramer@×××.de wrote:
>>>> Hi,
>>>>
>>>> from ancient times ;) I remember, that it is not advisable
>>>> to compile a linux kernel with more than one cpu core.
>>>>
>>>> Is that still true, or is it save to compile it with
>>>> "all you can eat" ::)) ?
>>>>
>>>> Cheers
>>>> Meino
>>>>
>>>>
>>>
>>> While I don't upgrade my kernel very often, since I don't reboot often
>>> either, I've used -j 6 for my 4 core CPU for a long time.  I'm pretty
>>> sure I've done that ever since I built this rig.  So far, no problems
>>> that I have seen.
>>>
>>> Dale
>>>
>>> :-)  :-)
>>>
>>
>> Great! Currently rebuilding the kernel with '-j7 ' :)
>
> I wonder, how does it make sure that a dependency is always compiled
> before  what depends on it, so the link and all that works?
>

The kernel is special - it's a completely self-contained body of code
with no external dependencies, so it is internally consistency almost as
a matter of course.

As for compiling the right things in the right order, the Makefiles take
care of that just like all other software with a build system. How does
the Makefile get made? Well, when you do make <something>config, you see
all those deps like how iwlwifi depends on 80211 which depends on
networking etc. That tells you the order things must be built in. Shove
that into a Makefile maker, and voila, Bob's your auntie. Build issues
tends to get fixed during the dev period so when Linux releases a kernel
there's an excellent chance it will build correctly.

FWIW, none of this is a specially difficult problem. It's the kind of
thing I'd expect bright CS students to be able to do at the end of the
first year



-- 
Alan McKinnon
alan.mckinnon@×××××.com