[ofa-general] Re: [PATCH 0 of 9] mmu notifier #v12

Andrea Arcangeli
2008-04-22T13:21:43Z

On Tue, Apr 22, 2008 at 08:01:20AM -0500, Robin Holt wrote:
> On Tue, Apr 22, 2008 at 02:00:56PM +0200, Andrea Arcangeli wrote:
> > On Tue, Apr 22, 2008 at 09:20:26AM +0200, Andrea Arcangeli wrote:
> > > invalidate_range_start {
> > > spin_lock(&kvm->mmu_lock);
> > >
> > > kvm->invalidate_range_count++;
> > > rmap-invalidate of sptes in range
> > >
> >
> > write_seqlock; write_sequnlock;
>
> I don't think you need it here since invalidate_range_count is already
> elevated which will accomplish the same effect.

Agreed, seqlock only in range_end should be enough. BTW, the fact
seqlock is needed regardless of invalidate_page existing or not,
really makes invalidate_page a no brainer not just from the core VM
point of view, but from the driver point of view too. The
kvm_page_fault logic would be the same even if I remove
invalidate_page from the mmu notifier patch but it'd run slower both
when armed and disarmed.