From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752624AbbJTHVz (ORCPT ); Tue, 20 Oct 2015 03:21:55 -0400 Received: from mail-pa0-f41.google.com ([209.85.220.41]:34642 "EHLO mail-pa0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752546AbbJTHVQ (ORCPT ); Tue, 20 Oct 2015 03:21:16 -0400 Date: Tue, 20 Oct 2015 16:21:09 +0900 From: Minchan Kim To: Andrew Morton , "Kirill A. Shutemov" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Rik van Riel , Mel Gorman , Michal Hocko , Johannes Weiner , Vlastimil Babka Subject: Re: [PATCH 0/5] MADV_FREE refactoring and fix KSM page Message-ID: <20151020072109.GD2941@bbox> References: <1445236307-895-1-git-send-email-minchan@kernel.org> <20151019100150.GA5194@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151019100150.GA5194@bbox> 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 Mon, Oct 19, 2015 at 07:01:50PM +0900, Minchan Kim wrote: > On Mon, Oct 19, 2015 at 03:31:42PM +0900, Minchan Kim wrote: > > Hello, it's too late since I sent previos patch. > > https://lkml.org/lkml/2015/6/3/37 > > > > This patch is alomost new compared to previos approach. > > I think this is more simple, clear and easy to review. > > > > One thing I should notice is that I have tested this patch > > and couldn't find any critical problem so I rebased patchset > > onto recent mmotm(ie, mmotm-2015-10-15-15-20) to send formal > > patchset. Unfortunately, I start to see sudden discarding of > > the page we shouldn't do. IOW, application's valid anonymous page > > was disappeared suddenly. > > > > When I look through THP changes, I think we could lose > > dirty bit of pte between freeze_page and unfreeze_page > > when we mark it as migration entry and restore it. > > So, I added below simple code without enough considering > > and cannot see the problem any more. > > I hope it's good hint to find right fix this problem. > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index d5ea516ffb54..e881c04f5950 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -3138,6 +3138,9 @@ static void unfreeze_page_vma(struct vm_area_struct *vma, struct page *page, > > if (is_write_migration_entry(swp_entry)) > > entry = maybe_mkwrite(entry, vma); > > > > + if (PageDirty(page)) > > + SetPageDirty(page); > > The condition of PageDirty was typo. I didn't add the condition. > Just added. > > SetPageDirty(page); I reviewed THP refcount redesign patch and It seems below patch fixes MADV_FREE problem. It works well for hours. >>From 104a0940b4c0f97e61de9fee0fd602926ff28312 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Tue, 20 Oct 2015 16:00:52 +0900 Subject: [PATCH] mm: mark head page dirty in split_huge_page In thp split in old THP refcount, we mappped all of pages (ie, head + tails) to pte_mkdirty and mark PG_flags to every tail pages. But with THP refcount redesign, we can lose dirty bit in page table and PG_dirty for head page if we want to free the THP page using migration_entry. It ends up discarding head page by madvise_free suddenly. This patch fixes it by mark the head page PG_dirty when VM splits the THP page. Signed-off-by: Minchan Kim --- mm/huge_memory.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index adccfb48ce57..7fbbd42554a1 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3258,6 +3258,7 @@ static void __split_huge_page(struct page *page, struct list_head *list) atomic_sub(tail_mapcount, &head->_count); ClearPageCompound(head); + SetPageDirty(head); spin_unlock_irq(&zone->lru_lock); unfreeze_page(page_anon_vma(head), head); -- 1.9.1