From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx169.postini.com [74.125.245.169]) by kanga.kvack.org (Postfix) with SMTP id A84066B0114 for ; Wed, 29 May 2013 10:09:13 -0400 (EDT) Message-ID: <51A60BE5.7010905@synopsys.com> Date: Wed, 29 May 2013 19:38:37 +0530 From: Vineet Gupta MIME-Version: 1.0 Subject: Re: [PATCH] mm: Fix the TLB range flushed when __tlb_remove_page() runs out of slots References: <1369832173-15088-1-git-send-email-vgupta@synopsys.com> <20130529140319.GK17767@MacBook-Pro.local> In-Reply-To: <20130529140319.GK17767@MacBook-Pro.local> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Catalin Marinas Cc: Vineet Gupta , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Mel Gorman , Hugh Dickins , Rik van Riel , David Rientjes , Peter Zijlstra , "linux-arch@vger.kernel.org" , Max Filippov 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 >> Cc: Andrew Morton >> Cc: Mel Gorman >> Cc: Hugh Dickins >> Cc: Rik van Riel >> Cc: David Rientjes >> Cc: Peter Zijlstra >> Cc: linux-mm@kvack.org >> Cc: linux-arch@vger.kernel.org >> Cc: Catalin Marinas >> Cc: Max Filippov >> --- >> 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. Ignoring all other threads, do we agree that the exiting code - if used in any situations is incorrect semantically ? -Vineet -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org