From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 73B866B0260 for ; Tue, 10 Oct 2017 01:50:49 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id v2so1963491pfa.4 for ; Mon, 09 Oct 2017 22:50:49 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id l89si8501884pfk.260.2017.10.09.22.50.47 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 09 Oct 2017 22:50:47 -0700 (PDT) Date: Tue, 10 Oct 2017 07:50:44 +0200 From: Michal Hocko Subject: Re: [RFC] a question about mlockall() and mprotect() Message-ID: <20171010055044.7biiltr7lvm554ad@dhcp22.suse.cz> References: <20170926081716.xo375arjoyu5ytcb@dhcp22.suse.cz> <59CA125C.8000801@huawei.com> <20170926090255.jmocezs6s3lpd6p4@dhcp22.suse.cz> <59CA1A57.5000905@huawei.com> <59CA1C6E.4010501@huawei.com> <6b38ed08-62cb-97b1-9f16-1fd8e272b137@suse.cz> <20170926110012.jiw6plglsyksj5mc@dhcp22.suse.cz> <59CB3C4D.9090609@huawei.com> <20171009182656.ynu7tdzb5uwp5xnr@dhcp22.suse.cz> <59DC20CC.1030509@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <59DC20CC.1030509@huawei.com> Sender: owner-linux-mm@kvack.org List-ID: To: Xishi Qiu Cc: Vlastimil Babka , Joonsoo Kim , Mel Gorman , Linux MM , LKML , zhong jiang , yeyunfeng , wanghaitao12@huawei.com, "Zhoukang (A)" On Tue 10-10-17 09:22:20, Xishi Qiu wrote: > On 2017/10/10 2:26, Michal Hocko wrote: > > > On Wed 27-09-17 13:51:09, Xishi Qiu wrote: > >> On 2017/9/26 19:00, Michal Hocko wrote: > >> > >>> On Tue 26-09-17 11:45:16, Vlastimil Babka wrote: > >>>> On 09/26/2017 11:22 AM, Xishi Qiu wrote: > >>>>> On 2017/9/26 17:13, Xishi Qiu wrote: > >>>>>>> This is still very fuzzy. What are you actually trying to achieve? > >>>>>> > >>>>>> I don't expect page fault any more after mlock. > >>>>>> > >>>>> > >>>>> Our apps is some thing like RT, and page-fault maybe cause a lot of time, > >>>>> e.g. lock, mem reclaim ..., so I use mlock and don't want page fault > >>>>> any more. > >>>> > >>>> Why does your app then have restricted mprotect when calling mlockall() > >>>> and only later adjusts the mprotect? > >>> > >>> Ahh, OK I see what is goging on. So you have PROT_NONE vma at the time > >>> mlockall and then later mprotect it something else and want to fault all > >>> that memory at the mprotect time? > >>> > >>> So basically to do > >>> --- > >>> diff --git a/mm/mprotect.c b/mm/mprotect.c > >>> index 6d3e2f082290..b665b5d1c544 100644 > >>> --- a/mm/mprotect.c > >>> +++ b/mm/mprotect.c > >>> @@ -369,7 +369,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, > >>> * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major > >>> * fault on access. > >>> */ > >>> - if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED && > >>> + if ((oldflags & (VM_WRITE | VM_LOCKED)) == VM_LOCKED && > >>> (newflags & VM_WRITE)) { > >>> populate_vma_page_range(vma, start, end, NULL); > >>> } > >>> > >> > >> Hi Michal, > >> > >> My kernel is v3.10, and I missed this code, thank you reminding me. > > > > I guess I didn't get your answer. Does the above diff resolves your > > problem? > > Hi Michal, > > This upstream patch 36f881883c57941bb32d25cea6524f9612ab5a2c has already > resolve my problem, thank you for your attention. OK, fair enough. But is does it make sense to extend this behavior to shared mappings as well? -- Michal Hocko SUSE Labs -- 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