On Sun, Mar 18, 2012 at 03:01:08PM -0700, Linus Torvalds wrote:
> On Sun, Mar 18, 2012 at 12:07 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> > - ? ? ? tlb_finish_mmu(&tlb, 0, end);
> > + ? ? ? tlb_finish_mmu(&tlb, 0, -1);
>
> Hmm. The fact that you drop the end pointer means that some
> architectures that optimize the TLB flushing for ranges now
> effectively can't do it any more.
>
> Now, I think it's only ia64 that really is affected, but it *might* matter.
>
> In particular, ia64 has some logic for "if you only flush one single
> region, you can optimize it", and the region sizes are in the
> terabytes. And I'm pretty sure you broke that - I'm just not entirely
> sure how much we care.
Nope - ia64 check explicitly for precisely that case:
static inline void
ia64_tlb_flush_mmu (struct mmu_gather *tlb, unsigned long start, unsigned long end)
{
unsigned int nr;
if (!tlb->need_flush)
return;
tlb->need_flush = 0;
if (tlb->fullmm) {
/*
* Tearing down the entire address space. This happens both as a result
* of exit() and execve(). The latter case necessitates the call to
* flush_tlb_mm() here.
*/
flush_tlb_mm(tlb->mm);
....
and if that condition is true, we don't even look at start or end.
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