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Message-ID: <CANZA+xgjxezRuu4N2JpXbXjpKCz7825x_ZmdOe-DuxtMzGix-A@mail.gmail.com> Date: Thu, 21 Feb 2013 10:25:20 +0800 From: common An <xx.kernel@...il.com> To: linux-kernel@...r.kernel.org, linux-mm@...ck.org, linaro-kernel@...ts.linaro.org, riel@...hat.com Subject: Re: What does the PG_swapbacked of page flags actually mean? On Wed, Feb 20, 2013 at 6:43 PM, common An <xx.kernel@...il.com> 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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