[Devel] Re: [PATCH 1/1] fix compile with CONFIG_CHECKPOINT_DEBUG=n

[Serge E. Hallyn]

Quoting Oren Laadan (orenl at librato.com):
> 
> 
> Serge E. Hallyn wrote:
> > On the one hand, compiling without checkpoing debug saves a
> > lot of kernel size:
> > 
> > with debug:
> > -rwxrwxr-x  1 hallyn hallyn  62391508 Oct 21 22:08 vmlinux
> > without debug:
> > -rwxrwxr-x  1 hallyn hallyn  62298077 Oct 21 22:33 vmlinux
> > 
> > OTOH the need for this patch just proves my point that we don't
> > want any more config options than we need (especially no
> > CONFIG_CHECKPOINT_LOGGING in addition to _DEBUG).
> > 
> > So that begs the question - is there something we can do to
> > avoid having to recompile the kernel to turn on debugging,
> > but not take up 100k of space in vmlinux?  Maybe get rid of
> > the ckpt_debugs altogether and instead provide pre-written
> > kprobe sets to turn on debugging at specific places?
> 
> What is the reason for the increase - the strings ? the extra
> inlined code ?  the passing of variables to printed ?

Half and half :)

Pulling out the 'current->pid' and task_pid_nr arguments in
_ckpt_debug to printk, but keeping the __func__ and __LINE__,
halves the overhead of CONFIG_CHECKPOINT_DEBUG from
78190 to 39809 bytes.

-serge
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