From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx150.postini.com [74.125.245.150]) by kanga.kvack.org (Postfix) with SMTP id C60246B0002 for ; Wed, 20 Feb 2013 21:25:21 -0500 (EST) Received: by mail-vb0-f46.google.com with SMTP id b13so5479071vby.33 for ; Wed, 20 Feb 2013 18:25:20 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: Date: Thu, 21 Feb 2013 10:25:20 +0800 Message-ID: Subject: Re: What does the PG_swapbacked of page flags actually mean? From: common An Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linaro-kernel@lists.linaro.org, riel@redhat.com On Wed, Feb 20, 2013 at 6:43 PM, common An wrote: > PG_swapbacked is a bit for page->flags. > > In kernel code, its comment is "page is backed by RAM/swap". But I couldn't > understand it. > 1. Does the RAM mean DRAM? How page is backed by RAM? > 2. When the page is page-out to swap file, the bit PG_swapbacked will be set > to demonstrate this page is backed by swap. Is it right? > 3. In general, when will call SetPageSwapBacked() to set the bit? >>From : http://www.gossamer-threads.com/lists/linux/kernel/840692#840692 Every anonymous, tmpfs or shared memory segment page is potentially swap backed. That is the whole point of the PG_swapbacked flag. A page from a filesystem like ext3 or NFS cannot suddenly turn into a swap backed page. This page "nature" is not changed during the lifetime of a page. But, I am still a little confusing. > > Could anybody kindly explain for me? > > Thanks very much. -- 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