From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753061AbbJ0Hj0 (ORCPT ); Tue, 27 Oct 2015 03:39:26 -0400 Received: from mail-pa0-f43.google.com ([209.85.220.43]:33983 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751454AbbJ0HjZ convert rfc822-to-8bit (ORCPT ); Tue, 27 Oct 2015 03:39:25 -0400 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 9.0 \(3094\)) Subject: Re: [PATCH 4/5] mm: simplify reclaim path for MADV_FREE From: yalin wang In-Reply-To: <20151027070903.GD26803@bbox> Date: Tue, 27 Oct 2015 15:39:16 +0800 Cc: Hugh Dickins , Andrew Morton , "open list:MEMORY MANAGEMENT" , lkml , Rik van Riel , Mel Gorman , Michal Hocko , Johannes Weiner , "Kirill A. Shutemov" , Vlastimil Babka Content-Transfer-Encoding: 8BIT Message-Id: <32537EDE-3EE6-4C44-B820-5BCAF7A5D535@gmail.com> References: <1445236307-895-1-git-send-email-minchan@kernel.org> <1445236307-895-5-git-send-email-minchan@kernel.org> <20151027070903.GD26803@bbox> To: Minchan Kim X-Mailer: Apple Mail (2.3094) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Oct 27, 2015, at 15:09, Minchan Kim wrote: > > Hello Yalin, > > Sorry for missing you in Cc list. > IIRC, mails to send your previous mail address(Yalin.Wang@sonymobile.com) > were returned. > > You added comment bottom line so I'm not sure what PageDirty you meant. > >> it is wrong here if you only check PageDirty() to decide if the page is freezable or not . >> The Anon page are shared by multiple process, _mapcount > 1 , >> so you must check all pt_dirty bit during page_referenced() function, >> see this mail thread: >> http://ns1.ske-art.com/lists/kernel/msg1934021.html > > If one of pte among process sharing the page was dirty, the dirtiness should > be propagated from pte to PG_dirty by try_to_unmap_one. > IOW, if the page doesn't have PG_dirty flag, it means all of process did > MADV_FREE. > > Am I missing something from you question? > If so, could you show exact scenario I am missing? > > Thanks for the interest. oh, yeah , that is right , i miss that , pte_dirty will propagate to PG_dirty , so that is correct . Generic to say this patch move set_page_dirty() from add_to_swap() to try_to_unmap(), i think can change a little about this patch: @@ -1476,6 +1446,8 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, ret = SWAP_FAIL; goto out_unmap; } + if (!PageDirty(page)) + SetPageDirty(page); if (list_empty(&mm->mmlist)) { spin_lock(&mmlist_lock); if (list_empty(&mm->mmlist)) i think this 2 lines can be removed , since pte_dirty have propagated to set_page_dirty() , we don’t need this line here , otherwise you will always dirty a AnonPage, even it is clean, then we will page out this clean page to swap partition one more , this is not needed. am i understanding correctly ? By the way, please change my mail address to yalin.wang2010@gmail.com in CC list . Thanks a lot. :)