On Wed, Feb 20, 2013 at 6:43 PM, common An <xx.kernel@xxxxxxxxx> 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@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>