From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f199.google.com (mail-qt0-f199.google.com [209.85.216.199]) by kanga.kvack.org (Postfix) with ESMTP id D6FD06B02FD for ; Fri, 16 Jun 2017 10:27:23 -0400 (EDT) Received: by mail-qt0-f199.google.com with SMTP id o41so36347261qtf.8 for ; Fri, 16 Jun 2017 07:27:23 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id a129si2076669qkd.180.2017.06.16.07.27.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Jun 2017 07:27:23 -0700 (PDT) Date: Fri, 16 Jun 2017 16:27:20 +0200 From: Andrea Arcangeli Subject: Re: [PATCHv2 3/3] mm: Use updated pmdp_invalidate() inteface to track dirty/accessed bits Message-ID: <20170616142720.GH11676@redhat.com> References: <20170615145224.66200-1-kirill.shutemov@linux.intel.com> <20170615145224.66200-4-kirill.shutemov@linux.intel.com> <20170616030250.GA27637@bbox> <20170616131908.3rxtm2w73gdfex4a@node.shutemov.name> <20170616135209.GA29542@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170616135209.GA29542@bbox> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: "Kirill A. Shutemov" , "Kirill A. Shutemov" , Andrew Morton , Vlastimil Babka , Vineet Gupta , Russell King , Will Deacon , Catalin Marinas , Ralf Baechle , "David S. Miller" , "Aneesh Kumar K . V" , Martin Schwidefsky , Heiko Carstens , linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Hello Minchan, On Fri, Jun 16, 2017 at 10:52:09PM +0900, Minchan Kim wrote: > > > > @@ -1995,8 +1984,6 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > > > > if (soft_dirty) > > > > entry = pte_mksoft_dirty(entry); > > > > } > > > > - if (dirty) > > > > - SetPageDirty(page + i); > > > > pte = pte_offset_map(&_pmd, addr); [..] > > split_huge_page set PG_dirty to all subpages unconditionally? > If it's true, yes, it doesn't break MADV_FREE. However, I didn't spot > that piece of code. What I found one is just __split_huge_page_tail > which set PG_dirty to subpage if head page is dirty. IOW, if the head > page is not dirty, tail page will be clean, too. > Could you point out what routine set PG_dirty to all subpages unconditionally? On a side note the snippet deleted above was useless, as long as there's one left hugepmd to split, the physical page has to be still compound and huge and as long as that's the case the tail pages PG_dirty bit is meaningless (even if set, it's going to be clobbered during the physical split). In short PG_dirty is only meaningful in the head as long as it's compound. The physical split in __split_huge_page_tail transfer the head value to the tails like you mentioned, that's all as far as I can tell. -- 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