kernel hcking

kernel hcking

[Vikram Rangnekar]

I'm a kernel newbie and just wanted to know what do most kernel hackers do
when working on the kernel say 2.5 when you make changes do u need to
recompile the kernel and reboot the machine to test your small modification
or do people use something like bochs. Also every time you makes changes in
the kernel it must be hell to recompile the whole thing do kernel hackers
just compile the specific file and link it into the kernel or something. Some
of these will be stupid questions to most of you but I am curious since I've
been working on the kernel lately and recompiling and rebooting is driving me
nuts

-- 
regards
Vikram (http://www.vicramresearch.com)

Re: kernel hcking

[Con Kolivas]

On Sat, 12 Apr 2003 01:07, Vikram Rangnekar wrote:
> I'm a kernel newbie and just wanted to know what do most kernel hackers do
> when working on the kernel say 2.5 when you make changes do u need to
> recompile the kernel and reboot the machine to test your small modification
> or do people use something like bochs. Also every time you makes changes in
> the kernel it must be hell to recompile the whole thing do kernel hackers
> just compile the specific file and link it into the kernel or something.
> Some of these will be stupid questions to most of you but I am curious
> since I've been working on the kernel lately and recompiling and rebooting
> is driving me nuts

Try cc cache
http://ccache.samba.org

Con

Re: kernel hcking

[John Bradford]

> I'm a kernel newbie and just wanted to know what do most kernel hackers do
> when working on the kernel say 2.5 when you make changes do u need to
> recompile the kernel and reboot the machine to test your small modification
> or do people use something like bochs.

A lot of developers have multiple physical machines, which makes
testing various different kernels a lot easier.

> Also every time you makes changes in the kernel it must be hell to
> recompile the whole thing

If you are testing kernels on a separate machine to the one you are
compiling on, and therefore not rebooting, it's not much of a problem
- with enough RAM, most or all of the kernel source will be cached,
and you can compile a kernel in three to five minutes on a fast
machine.

John.

Re: kernel hcking

[Antonio Vargas]

On Fri, Apr 11, 2003 at 05:07:09PM +0200, Vikram Rangnekar wrote:
> 
> I'm a kernel newbie and just wanted to know what do most kernel hackers do
> when working on the kernel say 2.5 when you make changes do u need to
> recompile the kernel and reboot the machine to test your small modification
> or do people use something like bochs. Also every time you makes changes in
> the kernel it must be hell to recompile the whole thing do kernel hackers
> just compile the specific file and link it into the kernel or something. Some
> of these will be stupid questions to most of you but I am curious since I've
> been working on the kernel lately and recompiling and rebooting is driving me
> nuts

I'm also newbie at actually coding on the kernel, and I've
been using user-mode-linux to try my patches... it's easy and clean,
just make a very small config so that the initial compile is
also fast.

Then, when you are doing incremental compiling, just do a
"make -j linux", this is very fast when you are not recompiling
all .o files since the makefile checks the last-modified date
for the .c files.

For maximum performance, also use ccache with (very important) the
cache directory on the same filesystem than the compile directory.
I keep a "compile" directory and a "ccache" directory at the same
level.

When testing with user-mode-linux, you can simply type
./linux and the new kernel boots in your terminal. If
you want to boot a real machine, I suggest you get a
second computer and boot it by loading the kernel off
the net, using tftp protocol.

Ping me if you want some more help at this last issue.

Greets and have fun!

Antonio.

Re: kernel hcking

[Antonio Vargas]

On Fri, Apr 11, 2003 at 04:24:37PM +0100, John Bradford wrote:
> > I'm a kernel newbie and just wanted to know what do most kernel hackers do
> > when working on the kernel say 2.5 when you make changes do u need to
> > recompile the kernel and reboot the machine to test your small modification
> > or do people use something like bochs.
> 
> A lot of developers have multiple physical machines, which makes
> testing various different kernels a lot easier.
> 
> > Also every time you makes changes in the kernel it must be hell to
> > recompile the whole thing
> 
> If you are testing kernels on a separate machine to the one you are
> compiling on, and therefore not rebooting, it's not much of a problem
> - with enough RAM, most or all of the kernel source will be cached,
> and you can compile a kernel in three to five minutes on a fast
> machine.

John, you mean a "make clean && make bzImage" takes you only about 4
minutes??? I would like to know more details about .config, machine
specs, compiler and so on :)

And no doubt having enough RAM to cache all the tree is really good :)

Greets, Antonio.

Re: kernel hcking

[John Bradford]

> John, you mean a "make clean && make bzImage" takes you only about 4
> minutes???

Yep.

Well, make distclean; cp /foo/bar/config .config; make oldconfig; make bzImage

> I would like to know more details about .config, machine specs,
> compiler and so on :)

That's on an Athlon XP 2200, 512 MB RAM, 7200 RPM disk, with a fairly
typical .config.

> And no doubt having enough RAM to cache all the tree is really good :)

Yep :-).

John.

Re: kernel hcking

[Jan-Benedict Glaw]

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On Fri, 2003-04-11 17:37:11 +0200, Antonio Vargas <wind@cocodriloo.com>
wrote in message <20030411153711.GE25862@wind.cocodriloo.com>:
> On Fri, Apr 11, 2003 at 04:24:37PM +0100, John Bradford wrote:
> > > Also every time you makes changes in the kernel it must be hell to
> > > recompile the whole thing
> > 
> > If you are testing kernels on a separate machine to the one you are
> > compiling on, and therefore not rebooting, it's not much of a problem
> > - with enough RAM, most or all of the kernel source will be cached,
> > and you can compile a kernel in three to five minutes on a fast
> > machine.
> 
> John, you mean a "make clean && make bzImage" takes you only about 4
> minutes??? I would like to know more details about .config, machine
> specs, compiler and so on :)

Um, take 1.5GB RAM and one of those dual athlon boards and you'll even
do a full compile in <5min...

MfG, JBG

-- 
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