From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx187.postini.com [74.125.245.187]) by kanga.kvack.org (Postfix) with SMTP id BBD186B0062 for ; Mon, 3 Dec 2012 19:00:10 -0500 (EST) Date: Tue, 4 Dec 2012 09:00:42 +0900 From: Minchan Kim Subject: Re: [RFC v2] Support volatile range for anon vma Message-ID: <20121204000042.GB20395@bbox> References: <1351560594-18366-1-git-send-email-minchan@kernel.org> <50AD739A.30804@linaro.org> <50B6E1F9.5010301@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50B6E1F9.5010301@linaro.org> Sender: owner-linux-mm@kvack.org List-ID: To: John Stultz Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Christoph Lameter , Android Kernel Team , Robert Love , Mel Gorman , Hugh Dickins , Dave Hansen , Rik van Riel , Dave Chinner , Neil Brown , Mike Hommey , Taras Glek , KOSAKI Motohiro , KAMEZAWA Hiroyuki On Wed, Nov 28, 2012 at 08:18:01PM -0800, John Stultz wrote: > On 11/21/2012 04:36 PM, John Stultz wrote: > >2) Being able to use this with tmpfs files. I'm currently trying > >to better understand the rmap code, looking to see if there's a > >way to have try_to_unmap_file() work similarly to > >try_to_unmap_anon(), to allow allow users to madvise() on mmapped > >tmpfs files. This would provide a very similar interface as to > >what I've been proposing with fadvise/fallocate, but just using > >process virtual addresses instead of (fd, offset) pairs. The > >benefit with (fd,offset) pairs for Android is that its easier to > >manage shared volatile ranges between two processes that are > >sharing data via an mmapped tmpfs file (although this actual use > >case may be fairly rare). I believe we should still be able to > >rework the ashmem internals to use madvise (which would provide > >legacy support for existing android apps), so then its just a > >question of if we could then eventually convince Android apps to > >use the madvise interface directly, rather then the ashmem unpin > >ioctl. > > Hey Minchan, > I've been playing around with your patch trying to better > understand your approach and to extend it to support tmpfs files. In > doing so I've found a few bugs, and have some rough fixes I wanted > to share. There's still a few edge cases I need to deal with (the > vma-purged flag isn't being properly handled through vma merge/split > operations), but its starting to come along. Hmm, my patch doesn't allow to merge volatile with another one by inserting VM_VOLATILE into VM_SPECIAL so I guess merge isn't problem. In case of split, __split_vma copy old vma to new vma like this *new = *vma; So the problem shouldn't happen, I guess. Did you see the real problem about that? > > Anyway, take a look at the tree here and let me know what you think. > http://git.linaro.org/gitweb?p=people/jstultz/android-dev.git;a=shortlog;h=refs/heads/dev/minchan-anonvol > > I'm sure much is wrong with the tree, but with it I can now mark > tmpfs file pages as volatile/nonvolatile and see them purged under > pressure. Unfortunately its not limited to tmpfs, so persistent > files will also work, but the state of the underlying files on purge > is undefined. Hopefully I can find a way to limit it to > non-persistent filesystems for now, and if needed find a way to > extend it to persistent filesystems in a sane way later. I will take a look. Thanks. > > thanks > -john > > -- > 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 -- Kind regards, Minchan Kim -- 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