From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx137.postini.com [74.125.245.137]) by kanga.kvack.org (Postfix) with SMTP id 880546B004D for ; Thu, 10 May 2012 22:51:40 -0400 (EDT) Received: by qcsd16 with SMTP id d16so2214715qcs.14 for ; Thu, 10 May 2012 19:51:39 -0700 (PDT) Message-ID: <4FAC7EBA.1080708@gmail.com> Date: Thu, 10 May 2012 22:51:38 -0400 From: KOSAKI Motohiro MIME-Version: 1.0 Subject: Re: [PATCH 2/2 v3] drm/exynos: added userptr feature. References: <1335188594-17454-4-git-send-email-inki.dae@samsung.com> <1336544259-17222-1-git-send-email-inki.dae@samsung.com> <1336544259-17222-3-git-send-email-inki.dae@samsung.com> <001501cd2e4d$c7dbc240$579346c0$%dae@samsung.com> <4FAB4AD8.2010200@kernel.org> <002401cd2e7a$1e8b0ed0$5ba12c70$%dae@samsung.com> <4FAB68CF.8000404@kernel.org> <4FAB782C.306@kernel.org> <003301cd2e89$13f78c00$3be6a400$%dae@samsung.com> <4FAC0091.7070606@gmail.com> <4FAC623E.7090209@kernel.org> In-Reply-To: <4FAC623E.7090209@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: KOSAKI Motohiro , Inki Dae , 'InKi Dae' , 'Jerome Glisse' , airlied@linux.ie, dri-devel@lists.freedesktop.org, kyungmin.park@samsung.com, sw0312.kim@samsung.com, linux-mm@kvack.org (5/10/12 8:50 PM), Minchan Kim wrote: > Hi KOSAKI, > > On 05/11/2012 02:53 AM, KOSAKI Motohiro wrote: > >>>>> let's assume that one application want to allocate user space memory >>>>> region using malloc() and then write something on the region. as you >>>>> may know, user space buffer doen't have real physical pages once >>>>> malloc() call so if user tries to access the region then page fault >>>>> handler would be triggered >>>> >>>> >>>> Understood. >>>> >>>>> and then in turn next process like swap in to fill physical frame >>>>> number >>>> into entry of the page faulted. >>>> >>>> >>>> Sorry, I can't understand your point due to my poor English. >>>> Could you rewrite it easiliy? :) >>>> >>> >>> Simply saying, handle_mm_fault would be called to update pte after >>> finding >>> vma and checking access right. and as you know, there are many cases to >>> process page fault such as COW or demand paging. >> >> Hmm. If I understand correctly, you guys misunderstand mlock. it doesn't >> page pinning >> nor prevent pfn change. It only guarantee to don't make swap out. e.g. > > > Symantic point of view, you're right but the implementation makes sure page pinning. > >> memory campaction >> feature may automatically change page physical address. > > > I tried it last year but decided drop by realtime issue. > https://lkml.org/lkml/2011/8/29/295 > > so I think mlock is a kind of page pinning. If elsewhere I don't realized is doing, that place should be fixed. > Or my above patch should go ahead. Thanks pointing out. I didn't realized your patch didn't merged. I think it should go ahead. think autonuma case, if mlock disable autonuma migration, that's bug. I don't think we can promise mlock don't change physical page. I wonder if any realtime guys page migration is free lunch. they should disable both auto migration and compaction. And, think if application explictly use migrate_pages(2) or admins uses cpusets. driver code can't assume such scenario doesn't occur, yes? -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org