Re: About git-bisect (was: Linux 2.6.28-rc7)

From: Francis Moreau
Date: Tue Dec 02 2008 - 16:53:17 EST

Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> writes:

> That said, the _best_ way to speed up your compile (whether bisecting or
> not) is to simply only compile the drivers and modules you actually need.

That's interesting because I recently tried to strip down my kernel
configuration but I met a problem: I usually don't know if I really
need a feature or not, and that's specially true when configuring the
network stuffs, since I'm not a network expert...

So I still have 254 modules and after recompiling my kernel, I did:

$ touch kernel/sched.c
$ time make -j4
MODPOST 254 modules
Kernel: arch/x86/boot/bzImage is ready (#109)

real 3m23.866s
user 0m35.006s
sys 0m15.698s

and here is the time I get if I recompile the kernel without touching
any files:

$ time make -j4
CHK include/linux/version.h
CHK include/linux/utsrelease.h
SYMLINK include/asm -> include/asm-x86
CALL scripts/
CHK include/linux/compile.h
dnsdomainname: Unknown host
CHK include/linux/version.h
make[2]: `scripts/unifdef' is up to date.
Building modules, stage 2.
Kernel: arch/x86/boot/bzImage is ready (#109)
MODPOST 254 modules

real 0m53.612s
user 0m17.996s
sys 0m9.752s

With these figures, I can confirm that doing bisection, even with 5
reboots, is painful.

> It takes me 16 seconds to compile my kernel (if it's all cached), and
> that's largely because I do _not_ compile one of the crazy distro kernels
> with thousands of totally irrelevant modules for my setup.

an other reason is perhaps you're using a computer that most common
mortal don't have ;)

Care to share your network configuration ;) ?


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