From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f42.google.com (mail-pa0-f42.google.com [209.85.220.42]) by kanga.kvack.org (Postfix) with ESMTP id C36446B0253 for ; Tue, 27 Oct 2015 02:58:28 -0400 (EDT) Received: by pasz6 with SMTP id z6so213173225pas.2 for ; Mon, 26 Oct 2015 23:58:28 -0700 (PDT) Received: from mail-pa0-x22f.google.com (mail-pa0-x22f.google.com. [2607:f8b0:400e:c03::22f]) by mx.google.com with ESMTPS id c17si59517340pbu.132.2015.10.26.23.58.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 26 Oct 2015 23:58:28 -0700 (PDT) Received: by pacfv9 with SMTP id fv9so222854698pac.3 for ; Mon, 26 Oct 2015 23:58:28 -0700 (PDT) Date: Tue, 27 Oct 2015 15:58:45 +0900 From: Minchan Kim Subject: Re: [PATCH 5/5] mm: mark stable page dirty in KSM Message-ID: <20151027065845.GC26803@bbox> References: <1445236307-895-1-git-send-email-minchan@kernel.org> <1445236307-895-6-git-send-email-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Hugh Dickins Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Rik van Riel , Mel Gorman , Michal Hocko , Johannes Weiner , "Kirill A. Shutemov" , Vlastimil Babka On Mon, Oct 26, 2015 at 07:23:12PM -0700, Hugh Dickins wrote: > On Mon, 19 Oct 2015, Minchan Kim wrote: > > > Stable page could be shared by several processes and last process > > could own the page among them after CoW or zapping for every process > > except last process happens. Then, page table entry of the page > > in last process can have no dirty bit and PG_dirty flag in page->flags. > > In this case, MADV_FREE could discard the page wrongly. > > For preventing it, we mark stable page dirty. > > I agree with the change, but found that comment (repeated in the source) > rather hard to follow. And it doesn't really do justice to the changes > you have made. > > This is not now a MADV_FREE thing, it's more general than that, even > if MADV_FREE is the only thing that takes advantage of it. I like > very much that you've made page reclaim sane, freeing non-dirty > anonymous pages instead of swapping them out, without having to > think of whether it's for MADV_FREE or not. > > Would you mind if we replace your patch by a re-commented version? > > [PATCH] mm: mark stable page dirty in KSM > > The MADV_FREE patchset changes page reclaim to simply free a clean > anonymous page with no dirty ptes, instead of swapping it out; but > KSM uses clean write-protected ptes to reference the stable ksm page. > So be sure to mark that page dirty, so it's never mistakenly discarded. > > Signed-off-by: Minchan Kim > Signed-off-by: Hugh Dickins Looks better than mine. I will include this in my patchset when I respin. Thanks! -- 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