On Sat, 2 Mar 2013, Simon Jeons wrote: > On 03/02/2013 09:42 AM, Hugh Dickins wrote: > > On Sat, 2 Mar 2013, Simon Jeons wrote: > > > In function __add_to_swap_cache if add to radix tree successfully will > > > result > > > in increase NR_FILE_PAGES, why? This is anonymous page instead of file > > > backed > > > page. > > Right, that's hard to understand without historical background. > > > > I think the quick answer would be that we used to (and still do) think > > of file-cache and swap-cache as two halves of page-cache. And then when > > shmem page should be treated as file-cache or swap-cache? It is strange since > it is consist of anonymous pages and these pages establish files. A shmem page is swap-backed file-cache, and it may get transferred to or from swap-cache: yes, it's a difficult and confusing case, as I said below. I would never call it "anonymous", but it is counted in /proc/meminfo's Active(anon) or Inactive(anon) rather than in (file), because "anon" there is shorthand for "swap-backed". > > So you'll find that shmem and swap are counted as file in some places > > and anon in others, and it's hard to grasp which is where and why, > > without remembering the history. Hugh -- 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>