On Wed, May 29, 2013 at 03:36:02PM +0100, Vineet Gupta wrote: > On 05/29/2013 07:59 PM, Catalin Marinas wrote: > > On Wed, May 29, 2013 at 03:08:37PM +0100, Vineet Gupta wrote: > >> On 05/29/2013 07:33 PM, Catalin Marinas wrote: > >>> On Wed, May 29, 2013 at 01:56:13PM +0100, Vineet Gupta wrote: > >>>> zap_pte_range loops from @addr to @end. In the middle, if it runs out of > >>>> batching slots, TLB entries needs to be flushed for @start to @interim, > >>>> NOT @interim to @end. > >>>> > >>>> Since ARC port doesn't use page free batching I can't test it myself but > >>>> this seems like the right thing to do. > >>>> Observed this when working on a fix for the issue at thread: > >>>> http://www.spinics.net/lists/linux-arch/msg21736.html > >>>> > >>>> Signed-off-by: Vineet Gupta <[email protected]> > >>>> Cc: Andrew Morton <[email protected]> > >>>> Cc: Mel Gorman <[email protected]> > >>>> Cc: Hugh Dickins <[email protected]> > >>>> Cc: Rik van Riel <[email protected]> > >>>> Cc: David Rientjes <[email protected]> > >>>> Cc: Peter Zijlstra <[email protected]> > >>>> Cc: [email protected] > >>>> Cc: [email protected] <[email protected]> > >>>> Cc: Catalin Marinas <[email protected]> > >>>> Cc: Max Filippov <[email protected]> > >>>> --- > >>>> mm/memory.c | 9 ++++++--- > >>>> 1 file changed, 6 insertions(+), 3 deletions(-) > >>>> > >>>> diff --git a/mm/memory.c b/mm/memory.c > >>>> index 6dc1882..d9d5fd9 100644 > >>>> --- a/mm/memory.c > >>>> +++ b/mm/memory.c > >>>> @@ -1110,6 +1110,7 @@ static unsigned long zap_pte_range(struct > >>>> mmu_gather *tlb, > >>>> spinlock_t *ptl; > >>>> pte_t *start_pte; > >>>> pte_t *pte; > >>>> + unsigned long range_start = addr; > >>>> > >>>> again: > >>>> init_rss_vec(rss); > >>>> @@ -1215,12 +1216,14 @@ again: > >>>> force_flush = 0; > >>>> > >>>> #ifdef HAVE_GENERIC_MMU_GATHER > >>>> - tlb->start = addr; > >>>> - tlb->end = end; > >>>> + tlb->start = range_start; > >>>> + tlb->end = addr; > >>>> #endif > >>>> tlb_flush_mmu(tlb); > >>>> - if (addr != end) > >>>> + if (addr != end) { > >>>> + range_start = addr; > >>>> goto again; > >>>> + } > >>>> } > >>> Isn't this code only run if force_flush != 0? force_flush is set to > >>> !__tlb_remove_page() and this function always returns 1 on (generic TLB) > >>> UP since tlb_fast_mode() is 1. There is no batching on UP with the > >>> generic TLB code. > >> Correct ! That's why the changelog says I couldn't test it on ARC port > >> itself :-) > >> > >> However based on the other discussion (Max's TLB/PTE inconsistency), as I > >> started > >> writing code to reuse this block to flush the TLB even for non forced > >> case, I > >> realized that what this is doing is incorrect and won't work for the > >> general flushing. > > An alternative would be to make sure the above block is always called > > when tlb_fast_mode(): > > > > diff --git a/mm/memory.c b/mm/memory.c > > index 6dc1882..f8b1f30 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -1211,7 +1211,7 @@ again: > > * the PTE lock to avoid doing the potential expensive TLB invalidate > > * and page-free while holding it. > > */ > > - if (force_flush) { > > + if (force_flush || tlb_fast_mode(tlb)) { > > force_flush = 0; > > I agree with tlb_fast_mode() addition (to solve Max's issue). The problem > however > is that when we hit this at the end of loop - @addr is already pointing to > @end so > range flush gets start = end - not what we really intended.
OK. So for this part your patch looks fine. Acked-by: Catalin Marinas <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
