Re: [Patch 0/7] Implement crashkernel=auto

[Amerigo Wang]

Eric W. Biederman wrote:
> Amerigo Wang <amwang@xxxxxxxxxx> writes:
>
>   
> > Eric W. Biederman wrote:
> >     
> > > Amerigo Wang <amwang@xxxxxxxxxx> writes:
> > >
> > >   
> > >       
> > > > > No the crashdump mechanism is useless because user space is already
> > > > > broken and unusable.
> > > > >       
> > > > >           
> > > > Again, why broken?
> > > >     
> > > >         
> > > To get a stock stat drive by hand I had to list about 5 kernel modules
> > > in the right magic order in /etc/kdump.conf
> > >
> > > Neither mount by label or mount by uuid when specified in /etc/kdump.conf
> > > I had to hack mkdumprd to get an initrd that even finds the proper disk
> > > to mount.
> > >   
> > >       
> > You are saying that there is some difficulty to make a initrd for kdump, but I
> > am sorry that I can't see any relations between this and my patch. What is your
> > point here?
> >     
>
> You are trying to make it easier for end users.
>
> I am saying the problem is in user space.
>
> I am saying also that the kernel doesn't have a clue what you are
> going to load with kexec on panic to handle panics.  Maybe it is a
> custom stand alone binary that only needs 5K.  So the kernel doesn't
> have a clue what the right size to reserve.
>   

So what? If you have 8G memory, would you mind 128M-5K memory to be wasted?

The kernel doesn't have to reserve the exact amount of memory that a 
kexec kernel will use, it just finds a big enough size for all cases 
which already assumes the physical memory is large enough.
> I think if what you were proposing was part of some coherent story for
> a complete implementation I would consider it more.  Instead this just
> appears to be a reaction to how frustrating the user space
> implementation is, and fixing things in the kernel instead of in user
> space.
>   

Yes, exactly, in fact I am doing another part which will allow us to 
take back of the reserved memory at run-time.


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