* Linus Torvalds <[email protected]> wrote:
> On Thu, 21 Jun 2007, Ingo Molnar wrote:
> >
> > I can understand why no data is saved by this change: gcc is
> > aligning the next field to a natural boundary anyway and we dont
> > really have arrays of spinlocks (fortunately).
>
> Actually, some data structures could well shrink.
>
> Look at "struct task_struct", for example. Right now it has two
> spinlocks right next to each other (alloc_lock and pi_lock).
yeah. We've got init_task's task-struct embedded in the vmlinux, but
it's aligned to 32 bytes, which probably hides this effect. We'd only
see it if the size change just happened to bring a key data structure
(which is also embedded in the vmlinux) just below a modulo 32 bytes
boundary. The chance for that is around 6:32 per 'merge' event. That
means that there cannot be all that many such cases ;-)
anyway, the shorter init sequence is worth it already.
Ingo
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