On Sat, Mar 21 2015, Rasmus Villemoes <[email protected]> wrote:
> With CONFIG_DEBUG_INFO_REDUCED, we do get quite a lot of debug info
> (around 22.7 MB for a defconfig+DEBUG_INFO_REDUCED). However, the
> "basenames must match" rule used by -femit-struct-debug-baseonly
> option means that we miss some core data structures, such as struct
> {device, file, inode, mm_struct, page} etc.
>
> We can easily get these included as well, while still getting the
> benefits of CONFIG_DEBUG_INFO_REDUCED (faster build times and smaller
> individual object files): All it takes is a dummy translation unit
> including a few strategic headers and compiled with a flag overriding
> -femit-struct-debug-baseonly.
>
> This increases the size of .debug_info by ~0.3%, but these 90 KB
> contain some rather useful info.
>
Any comments on this patch? I know it's a little hacky, but I do find it
rather useful. For example, I just noticed that pahole shows this
struct audit_names {
struct list_head list; /* 0 0 */
/* XXX 16 bytes hole, try to pack */
when applied to a vmlinux built with DEBUG_INFO_REDUCED, since debug
info for struct list_head is not included. The same is true for a lot of
other types which are often embedded in structs (e.g. spinlock_t and
atomic_t). I could of course just compile without DEBUG_INFO_REDUCED,
but the time and space savings of that are real and sad to lose (my tree
is 1.8 GB larger when I compile without it).
Rasmus
On Thu, Jun 11, 2015 at 02:32:48PM +0200, Rasmus Villemoes wrote:
> On Sat, Mar 21 2015, Rasmus Villemoes <[email protected]> wrote:
>
> > With CONFIG_DEBUG_INFO_REDUCED, we do get quite a lot of debug info
> > (around 22.7 MB for a defconfig+DEBUG_INFO_REDUCED). However, the
> > "basenames must match" rule used by -femit-struct-debug-baseonly
> > option means that we miss some core data structures, such as struct
> > {device, file, inode, mm_struct, page} etc.
> >
> > We can easily get these included as well, while still getting the
> > benefits of CONFIG_DEBUG_INFO_REDUCED (faster build times and smaller
> > individual object files): All it takes is a dummy translation unit
> > including a few strategic headers and compiled with a flag overriding
> > -femit-struct-debug-baseonly.
> >
> > This increases the size of .debug_info by ~0.3%, but these 90 KB
> > contain some rather useful info.
> >
>
> Any comments on this patch? I know it's a little hacky, but I do find it
> rather useful. For example, I just noticed that pahole shows this
I applied it to kbuild.git#kbuild now. It indeed can be quite useful.
Michal