From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B0A64C4321D for ; Thu, 23 Aug 2018 19:36:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 465952147A for ; Thu, 23 Aug 2018 19:36:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 465952147A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726522AbeHWXHQ (ORCPT ); Thu, 23 Aug 2018 19:07:16 -0400 Received: from mx2.suse.de ([195.135.220.15]:60508 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725979AbeHWXHQ (ORCPT ); Thu, 23 Aug 2018 19:07:16 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 2C0F7ADA9; Thu, 23 Aug 2018 19:36:04 +0000 (UTC) Date: Thu, 23 Aug 2018 21:36:00 +0200 From: Michal Hocko To: Mike Kravetz Cc: kbuild test robot , kbuild-all@01.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A . Shutemov" , =?iso-8859-1?B?Suly9G1l?= Glisse , Vlastimil Babka , Naoya Horiguchi , Davidlohr Bueso , Andrew Morton , stable@vger.kernel.org Subject: Re: [PATCH v3 1/2] mm: migration: fix migration of huge PMD shared pages Message-ID: <20180823193600.GV29735@dhcp22.suse.cz> References: <20180821205902.21223-2-mike.kravetz@oracle.com> <201808220831.eM0je51n%fengguang.wu@intel.com> <975b740d-26a6-eb3f-c8ca-1a9995d0d343@oracle.com> <20180823124855.GI29735@dhcp22.suse.cz> <12ea5339-f2b1-62b4-6d37-57d737fac34a@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 23-08-18 10:56:30, Mike Kravetz wrote: > On 08/23/2018 10:01 AM, Mike Kravetz wrote: > > On 08/23/2018 05:48 AM, Michal Hocko wrote: > >> On Tue 21-08-18 18:10:42, Mike Kravetz wrote: > >> [...] > >> > >> OK, after burning myself when trying to be clever here it seems like > >> your proposed solution is indeed simpler. > >> > >>> +bool huge_pmd_sharing_possible(struct vm_area_struct *vma, > >>> + unsigned long *start, unsigned long *end) > >>> +{ > >>> + unsigned long check_addr = *start; > >>> + bool ret = false; > >>> + > >>> + if (!(vma->vm_flags & VM_MAYSHARE)) > >>> + return ret; > >>> + > >>> + for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) { > >>> + unsigned long a_start = check_addr & PUD_MASK; > >>> + unsigned long a_end = a_start + PUD_SIZE; > >> > >> I guess this should be rather in HPAGE_SIZE * PTRS_PER_PTE units as > >> huge_pmd_unshare does. > > > > Sure, I can do that. > > On second thought, this is more similar to vma_shareable() which uses > PUD_MASK and PUD_SIZE. In fact Kirill asked me to put in a common helper > for this and vma_shareable. So, I would prefer to leave it as PUD* unless > you feel strongly. I don't > IMO, it would make more sense to change this in huge_pmd_unshare as PMD > sharing is pretty explicitly tied to PUD_SIZE. But, that is a future cleanup. Fair enough. I didn't realize we are PUD explicit elsewhere. So if you plan to update huge_pmd_unshare to be in sync then no objections from me at all. I merely wanted to be in sync with this because it is a central point to look at wrt pmd sharing. -- Michal Hocko SUSE Labs