Minimal Kernel Config for a F14 KVM guest

[David Quigley]

Hello,
    I will be teaching a one day class in a few weeks and I am going to 
have the students do some kernel programming. Since it is only a one day 
course I need to pack as much info into it as possible so I would like 
to minimize the build times as much as possible. The modifications that 
they will be making will be touching core kernel headers so it will have 
to rebuild almost all of the kernel every time. Because of this I'd like 
to get a kernel config that can get F14 booting (the minimal install) in 
KVM with the shortest build time possible. I've gotten the build down to 
9 minutes and 55 seconds but I would like it sub 5 minutes. Does anyone 
have or know of a place where I can find a bare minimum config. I've 
been working on trimming down the stock F14 kernel but there is so much 
to go through I'm thinking it might be best to build it up from an 
allnoconfig instead.

Dave

[Eamon Walsh]

On 07/01/2011 11:49 AM, David Quigley wrote:
>   On Fri, 01 Jul 2011 16:01:32 +0100, agraham wrote:
> > On 07/01/2011 04:12 AM, Dave Quigley wrote:
> >> Hello,
> >>      I will be teaching a one day class in a few weeks and I am 
> >> going to
> >> have the students do some kernel programming. Since it is only a one 
> >> day
> >> course I need to pack as much info into it as possible so I would 
> >> like
> >> to minimize the build times as much as possible. The modifications 
> >> that
> >> they will be making will be touching core kernel headers so it will 
> >> have
> >> to rebuild almost all of the kernel every time. Because of this I'd 
> >> like
> >> to get a kernel config that can get F14 booting (the minimal 
> >> install) in
> >> KVM with the shortest build time possible. I've gotten the build 
> >> down to
> >> 9 minutes and 55 seconds but I would like it sub 5 minutes. Does 
> >> anyone
> >> have or know of a place where I can find a bare minimum config. I've
> >> been working on trimming down the stock F14 kernel but there is so 
> >> much
> >> to go through I'm thinking it might be best to build it up from an
> >> allnoconfig instead.
> >>
> >> Dave
> > When making the kernel use make -j8 (assuming you have 8 cores) that
> > should reduce your time by running 8 parallel processes, in addition,
> > install ccache, that only compiles the code if it has changed or is
> > dependant on some other change, this should result in recompile of 
> > only
> > a few mins.
> >
> > Albert.
>   I doubt that people will be allocating 8 cores to a VM. I have 2 cores 
>   and 1GB of memory allocated at the moment and use -j3 to compile. The 
>   problem is they will be touching security.h which in one way or another 
>   is pretty much included by every source file in the Linux kernel so 
>   ccache won't be of much help (my normal dev box has ccache installed and 
>   it doesn't save me much time). The biggest way to cut down on time seems 
>   to be remove all the drivers that I can from being built. I think I have 
>   this almost complete. It would be nice if there was a make kvmconfig 
>   which gave you the base for an x86 or x86_64 kvm kernel config and then 
>   you can turn on whatever else you want filesystem and driver wise for 
>   passthrough devices.
>
>   Dave
>  
Maybe you could try building allmodconfig, then boot the kernel and lsmod to see what has
been loaded.  Then disable everything except for those modules.

--Eamon


-- 

Eamon Walsh 
National Security Agency

[David Quigley]

 On Fri, 01 Jul 2011 16:01:32 +0100, agraham wrote:
>  On 07/01/2011 04:12 AM, Dave Quigley wrote:
> > Hello,
> >      I will be teaching a one day class in a few weeks and I am 
> > going to
> > have the students do some kernel programming. Since it is only a one 
> > day
> > course I need to pack as much info into it as possible so I would 
> > like
> > to minimize the build times as much as possible. The modifications 
> > that
> > they will be making will be touching core kernel headers so it will 
> > have
> > to rebuild almost all of the kernel every time. Because of this I'd 
> > like
> > to get a kernel config that can get F14 booting (the minimal 
> > install) in
> > KVM with the shortest build time possible. I've gotten the build 
> > down to
> > 9 minutes and 55 seconds but I would like it sub 5 minutes. Does 
> > anyone
> > have or know of a place where I can find a bare minimum config. I've
> > been working on trimming down the stock F14 kernel but there is so 
> > much
> > to go through I'm thinking it might be best to build it up from an
> > allnoconfig instead.
> >
> > Dave
>
>  When making the kernel use make -j8 (assuming you have 8 cores) that
>  should reduce your time by running 8 parallel processes, in addition,
>  install ccache, that only compiles the code if it has changed or is
>  dependant on some other change, this should result in recompile of 
>  only
>  a few mins.
>
>  Albert. 
 I doubt that people will be allocating 8 cores to a VM. I have 2 cores 
 and 1GB of memory allocated at the moment and use -j3 to compile. The 
 problem is they will be touching security.h which in one way or another 
 is pretty much included by every source file in the Linux kernel so 
 ccache won't be of much help (my normal dev box has ccache installed and 
 it doesn't save me much time). The biggest way to cut down on time seems 
 to be remove all the drivers that I can from being built. I think I have 
 this almost complete. It would be nice if there was a make kvmconfig 
 which gave you the base for an x86 or x86_64 kvm kernel config and then 
 you can turn on whatever else you want filesystem and driver wise for 
 passthrough devices.

 Dave

[agraham]

On 07/01/2011 04:12 AM, Dave Quigley wrote:
>  Hello,
>       I will be teaching a one day class in a few weeks and I am going to
>  have the students do some kernel programming. Since it is only a one day
>  course I need to pack as much info into it as possible so I would like
>  to minimize the build times as much as possible. The modifications that
>  they will be making will be touching core kernel headers so it will have
>  to rebuild almost all of the kernel every time. Because of this I'd like
>  to get a kernel config that can get F14 booting (the minimal install) in
>  KVM with the shortest build time possible. I've gotten the build down to
>  9 minutes and 55 seconds but I would like it sub 5 minutes. Does anyone
>  have or know of a place where I can find a bare minimum config. I've
>  been working on trimming down the stock F14 kernel but there is so much
>  to go through I'm thinking it might be best to build it up from an
>  allnoconfig instead.
>
>  Dave 
When making the kernel use make -j8 (assuming you have 8 cores) that 
should reduce your time by running 8 parallel processes, in addition, 
install ccache, that only compiles the code if it has changed or is 
dependant on some other change, this should result in recompile of only 
a few mins.

Albert.