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 <vgupta@xxxxxxxxxxxx> > >> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > >> Cc: Mel Gorman <mgorman@xxxxxxx> > >> Cc: Hugh Dickins <hughd@xxxxxxxxxx> > >> Cc: Rik van Riel <riel@xxxxxxxxxx> > >> Cc: David Rientjes <rientjes@xxxxxxxxxx> > >> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > >> Cc: linux-mm@xxxxxxxxx > >> Cc: linux-arch@xxxxxxxxxxxxxxx <linux-arch@xxxxxxxxxxxxxxx> > >> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > >> Cc: Max Filippov <jcmvbkbc@xxxxxxxxx> > >> --- > >> 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; #ifdef HAVE_GENERIC_MMU_GATHER > Ignoring all other threads, do we agree that the exiting code - if used in any > situations is incorrect semantically ? It is incorrect unless there are requirements for arch_leave_lazy_mmu_mode() to handle the TLB invalidation (it doesn't look like it's widely implemented though). -- Catalin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>