From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752178AbaLAALo (ORCPT ); Sun, 30 Nov 2014 19:11:44 -0500 Received: from LGEMRELSE7Q.lge.com ([156.147.1.151]:35127 "EHLO lgemrelse7q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751927AbaLAALm (ORCPT ); Sun, 30 Nov 2014 19:11:42 -0500 X-Original-SENDERIP: 10.177.220.156 X-Original-MAILFROM: minchan@kernel.org Date: Mon, 1 Dec 2014 09:11:55 +0900 From: Minchan Kim To: Michal Hocko Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michael Kerrisk , linux-api@vger.kernel.org, Hugh Dickins , Johannes Weiner , Rik van Riel , KOSAKI Motohiro , Mel Gorman , Jason Evans , zhangyanfei@cn.fujitsu.com, "Kirill A. Shutemov" , Andrea Arcangeli , "Kirill A. Shutemov" Subject: Re: [PATCH v17 7/7] mm: Don't split THP page when syscall is called Message-ID: <20141201001155.GA11340@bbox> References: <1413799924-17946-1-git-send-email-minchan@kernel.org> <1413799924-17946-8-git-send-email-minchan@kernel.org> <20141127154921.GA11051@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20141127154921.GA11051@dhcp22.suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 27, 2014 at 04:49:21PM +0100, Michal Hocko wrote: > On Mon 20-10-14 19:12:04, Minchan Kim wrote: > > We don't need to split THP page when MADV_FREE syscall is > > called. It could be done when VM decide really frees it so > > we could avoid unnecessary THP split. > > > > Cc: Andrea Arcangeli > > Acked-by: Rik van Riel > > Acked-by: Kirill A. Shutemov > > Signed-off-by: Minchan Kim > > Other than a minor comment below > Reviewed-by: Michal Hocko Thanks! > > > --- > > include/linux/huge_mm.h | 4 ++++ > > mm/huge_memory.c | 35 +++++++++++++++++++++++++++++++++++ > > mm/madvise.c | 21 ++++++++++++++++++++- > > mm/rmap.c | 8 ++++++-- > > mm/vmscan.c | 28 ++++++++++++++++++---------- > > 5 files changed, 83 insertions(+), 13 deletions(-) > > > [...] > > diff --git a/mm/madvise.c b/mm/madvise.c > > index a21584235bb6..84badee5f46d 100644 > > --- a/mm/madvise.c > > +++ b/mm/madvise.c > > @@ -271,8 +271,26 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, > > spinlock_t *ptl; > > pte_t *pte, ptent; > > struct page *page; > > + unsigned long next; > > + > > + next = pmd_addr_end(addr, end); > > + if (pmd_trans_huge(*pmd)) { > > + if (next - addr != HPAGE_PMD_SIZE) { > > +#ifdef CONFIG_DEBUG_VM > > + if (!rwsem_is_locked(&mm->mmap_sem)) { > > + pr_err("%s: mmap_sem is unlocked! addr=0x%lx end=0x%lx vma->vm_start=0x%lx vma->vm_end=0x%lx\n", > > + __func__, addr, end, > > + vma->vm_start, > > + vma->vm_end); > > + BUG(); > > + } > > +#endif > > Why is this code here? madvise_free_pte_range is called only from the > madvise path and we are holding mmap_sem and relying on that for regular > pages as well. Make sense. >>From 2ecc213a2c3634cbee7529055fd6348b03307ed5 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Mon, 1 Dec 2014 09:07:18 +0900 Subject: [PATCH] mm: remove lock validation check for MADV_FREE Curretnly, madvise_free_pte_range is called only madvise path which already holds an mmap_sem so it's pointless to add the lock validation check. Signed-off-by: Minchan Kim --- mm/madvise.c | 13 ++----------- 1 file changed, 2 insertions(+), 11 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index dc024effa9bf..6fc9b8298da1 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -275,18 +275,9 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, next = pmd_addr_end(addr, end); if (pmd_trans_huge(*pmd)) { - if (next - addr != HPAGE_PMD_SIZE) { -#ifdef CONFIG_DEBUG_VM - if (!rwsem_is_locked(&mm->mmap_sem)) { - pr_err("%s: mmap_sem is unlocked! addr=0x%lx end=0x%lx vma->vm_start=0x%lx vma->vm_end=0x%lx\n", - __func__, addr, end, - vma->vm_start, - vma->vm_end); - BUG(); - } -#endif + if (next - addr != HPAGE_PMD_SIZE) split_huge_page_pmd(vma, addr, pmd); - } else if (!madvise_free_huge_pmd(tlb, vma, pmd, addr)) + else if (!madvise_free_huge_pmd(tlb, vma, pmd, addr)) goto next; /* fall through */ } -- 2.0.0 -- Kind regards, Minchan Kim