Messages in this thread | | | Date | Sat, 02 Mar 2013 12:06:46 +0800 | From | Simon Jeons <> | Subject | Re: [PATCH] add extra free kbytes tunable |
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On 03/02/2013 11:08 AM, Hugh Dickins wrote: > 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".
Oh, I see. Thanks. :)
> >>> 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
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