From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 2285E6B0069 for ; Wed, 27 Sep 2017 01:51:47 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id b9so14407168wra.3 for ; Tue, 26 Sep 2017 22:51:47 -0700 (PDT) Received: from szxga05-in.huawei.com (szxga05-in.huawei.com. [45.249.212.191]) by mx.google.com with ESMTPS id w5si2753877wma.208.2017.09.26.22.51.44 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 26 Sep 2017 22:51:45 -0700 (PDT) Message-ID: <59CB3C4D.9090609@huawei.com> Date: Wed, 27 Sep 2017 13:51:09 +0800 From: Xishi Qiu MIME-Version: 1.0 Subject: Re: [RFC] a question about mlockall() and mprotect() References: <59CA0847.8000508@huawei.com> <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> In-Reply-To: <20170926110012.jiw6plglsyksj5mc@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Vlastimil Babka , Joonsoo Kim , Mel Gorman , Linux MM , LKML , zhong jiang , yeyunfeng , wanghaitao12@huawei.com, "Zhoukang (A)" 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. Thanks, Xishi Qiu -- 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